Paul Ryan's vice presidential acceptance speech ran into a lot of trouble with fact-checkers and journalists.
It seemed like some reporters' heads were going to explode on Twitter as Ryan spoke. For instance, he blasted President Obama for not doing more to keep a GM plant in his hometown open. The problem was that the plant closed before Obama took office. He also criticized Obama for rejecting recommendations from a debt commission that he himself sat on, and whose findings he also rejected.
ABC's Jake Tapper was one of a nearly infinite amount of reporters tweeting these points:

Jake Tapper

this new debt commission Ryan is extoling? Ryan was on it and voted against its report.

The New Yorker's Atul Gawande was even more direct:

Atul Gawande

Ryan's outright, unflinching dishonesty on Medicare, GM, Simpson-Bowles, among others is revelatory -- a total discarding of pretense.

The Washington Post flatly said, "Ryan misleads on GM plant closing."
Some media watchers expressed initital frustration at the lack of fact-checking they were seeing on television during Ryan's speech:

James Poniewozik

Seriously, if my Twitter feed, Politifact &c can fact-ck convention in real time, isn't it irresponsible for TV crawls NOT to?

On CNN, Wolf Blitzer and Erin Burnett began by slightly skirting the issue immediately after the speech.
"I marked seven or eight points I'm sure the fact checkers will have some opportunities to dispute if they want to go forward," Blitzer said. "I'm sure they will." He did not specify what the points were.
After a correspondent's interview with Ryan's family — and a fair amount of criticism — Blitzer noted that he had been getting emails from Democrats and others about what, in his words, "they claim were falsehoods, misleading statements, lies, if you will, that were made by Paul Ryan. And I guess that fact-checking is only beginning."
John King then made the point about the GM plant, and Gloria Borger brought up the debt commission issue. Panelist David Gergen took a different tack.
"I think these factual checks are really important," Gergen said. "But this was a speech about big ideas."
This is not to say that Ryan got overwhelmingly negative reviews. CNN's Candy Crowley said he brought a "spark" to the convention hall. "This was the speech they were waiting for," she added. Burnett called the speech "precise, clear and passionate."

The reality is that Obama promised to help that factory retool in new industries. The factory technically is not closed, it is just shut down on standby, as were two other GM factories, one of which has reopened already in Michigan, Jaynesville is set to be the next to reopen (unless something changes) and another factory in Tennessee that was on standby and has expanded into full production. Jaynesville is set to reopen as demand continues for the successful new hybrid and smaller vehicles; GM production, thanks in large part to Obama, is continuing to thrive and grow again.

From ChicagoMag.com:

It's a reference to this passage in Ryan's speech:
My home state voted for President Obama. When he talked about change, many people liked the sound of it, especially in Janesville, where we were about to lose a major factory.
A lot of guys I went to high school with worked at that GM plant. Right there at that plant, candidate Obama said: “I believe that if our government is there to support you … this plant will be here for another hundred years.” That’s what he said in 2008.
Well, as it turned out, that plant didn’t last another year. It is locked up and empty to this day. And that’s how it is in so many towns today, where the recovery that was promised is nowhere in sight.
What actually happened is a bit more complicated.
On February 13, 2008, early in the campaign, Obama gave a speech at the GM plant in Janesville, several months before the closing of the plant was announced. And he said this:
I know that General Motors received some bad news yesterday, and I know how hard your Governor has fought to keep jobs in this plant. But I also know how much progress you’ve made – how many hybrids and fuel-efficient vehicles you’re churning out. And I believe that if our government is there to support you, and give you the assistance you need to re-tool and make this transition, that this plant will be here for another hundred years. The question is not whether a clean energy economy is in our future, it’s where it will thrive.
In context, Obama wasn't speaking so much about the auto bailout (which was just gearing up) as the idea that clean-energy investment could allow Janesville to remake its industrial sector, as made clear by the two previous paragraphs:
I believe that we can create millions of those jobs around a clean, renewable energy future. A few hours northeast of here is the city of Manitowoc [MAN-a-ta-WOC]. For over a century, it was the home of Mirro manufacturing – a company that provided thousands of jobs and plenty of business. In 2003, Mirro closed its doors for good after losing thousands of jobs to Mexico.
But in the last few years, something extraordinary has happened. Thanks to the leadership of Governor Doyle and Mayor Kevin Crawford, Manitowoc has re-trained its workers and attracted new businesses and new jobs. Orion Energy Systems works with companies to reduce their electricity use and carbon emissions. And Tower Tech is now making wind turbines that are being sold all over the world. Hundreds of people have found new work, and unemployment has been cut in half.
It wasn't a promise to keep the factory making cars; it was an expressed belief that a sweeping energy policy could give the town the resources to produce something else, like passenger rail cars.
Two days before Christmas, 10 months after his speech and three months before Obama would become president, the Janesville factory ceased to manufacture SUVs, as virtually all the plant's employees had been or were laid off that day; 50 stayed in the massive plant until late April, making trucks for Izuzu.
*******

It is worth noting that, like the rest of the right that is in the pocket of dirty coal and big oil, Paul Ryan opposes any efforts to switch this country off of fossil fuels, which are expensive, and being rapidly depleted.  But Ryan is beholden to big oil money, like the Koch brothers, so he opposes funding anything that decreases spending on oil, either directly as oil subsidies, or on petroleum fuels demand. Ryan is possibly even MORE the Koch brothers' bought and paid for 'boy' than Romney.

From that same article above:
Since then, the plant has remained in limbo, and the Janesville Gazette has continued to follow the now-quiet saga. In 2010, GM signaled that it would move work to one of its two standby plants, the other in Spring Hill, Tennessee—which, at the time, was not entirely idled, but operating below production. In 2011, GM reopened the Spring Hill plant, keeping Janesville on standby.
It's still owned by GM, and still in standby mode.
Ryan's comments on the Janesville plant were deceptive, but rather than obscuring a simple truth, they obscure a complex web of economics and politics. The plant closed under George W. Bush, but it's remained in play as a GM plant into the Obama administration—which you could view as giving some weight to Ryan's charge, but it's also limited the use of the plant to re-tool in the way that Obama originally proposed as a candidate. The auto-industry bailout did aid GM in saving jobs, including the jobs of Janesville plant employees, but only for those who relocated; the jobs were lost to Janesville itself. It's possible that, had the economy recovered more quickly, GM would have the demand required to bring the Janesville plant back online, as was suggested in late 2011, but that also reflects back on Ryan's support for the auto bailout versus his opposition to Obama's stimulus package. And the unemployment rate in Janesville has improved greatly since early 2009, though it remains above the state's unemployment rate.
The facts aren't what Ryan presented last night, but the truth is more complicated than the bare facts.