A post by Mihai Patrascu brought up the difficult issue of how to deal with papers that may or may not be correct when on a program committee. This is, clearly, a difficult question, and can lead to tremendous difficulties, as it is often not a simple task to determine correctness.
One approach is when an issue arises to inform the author(s) and ask them to clear up the issue. I recommend this, but it is not always functional; there may be disagreements between the author and the reviewers, and there is usually a limited amount of time to settle the problem.
Also, this seems to set up an onus on the author that may be unfair: you must convince us (outside what you've already written) that your proofs are correct. Now, that might not sound like an unfair onus, but for a difficult proof it may be very challenging, particularly since initially all that's been asked for (in most conferences) is a 10 page abstract and not the "final" version. Moreover, it's unfair because it's not something you're really asking of all the other authors. Sure, nominally you are, but papers with bugs get through often enough. Sometimes we make mistakes, and arguably there is some unfairness in a policy that insists that suspicious paper X must now be proven until all reviewers are fully satisfied while papers that didn't raise suspicions pass right on through.
As I've mentioned, I think the main job of the PC is to prioritize what papers get in a conference, and a secondary job is to give feedback to the authors. As part of that job, naturally, we want to throw out papers that are wrong and let the authors know about mistakes. But my argument is that conferences (and PCs) are not designed to accurately tell if papers are completely correct. If they were, I wouldn't have 45 papers to consider in a bit over a month, and I wouldn't be given papers on topics like quantum computing to judge. Ensuring correctness is nominally what journals are for, and that's why (in general) journal articles can take more time to review, and why one seeks experts for reviewing.
I'm not sure what a good solution is, and I'm not advocating blindly giving benefit of the doubt to papers that appear wrong. But there should be a high-level understanding that the conference procedure is inherently noisy. Mistaken proofs might be published. Perhaps the problem we should turn our attention to is how, as a community, we handle these errors, including arranging for such errors to be corrected or noted (by the authors or otherwise) in an appropriate fashion.