Ugh, this is literally keeping me up at nights. Viva went fine, everything's signed off on, but then a few days later as I was revising the dissertation I found an horrible error. My dissertation is basically qualitative political science; for one particular legal issue that I basically created the first comprehensive history of, I found out that it didn't end when I thought, and has been going on since with important stuff happening recently. If I hadn't caught it recently (and it was almost by pure chance that I did) I would have published this and destroyed my reputation right at the beginning of my career. The worst part is it was my "cheat" chapter -- basically it dealt with my prior professional field, so I don't even have the "newbie PhD" excuse. It doesn't change the central argument -- it actually supports it that these things have been happening -- but it just seems inexcusably careless.

Mentally I am having tremendous trouble dealing with this. I told my advisor but I don't think he gets the scope of this mistake. Another committee member who is closer to that issue probably will, though he's already signed off on it. It kind of takes a way a lot of the pride over finally getting the PhD. Anyone else ever deal with this kind of thing? I mean this won't (can't really) stop me from getting the degree, but now I feel like it's kind of a hollow victory.

I think most of us have gone through this at some point or another. Honestly, it doesn't matter, your viva is done, everything is finished. When you publish, just add in what you should have added in. No one will read your thesis in sufficient detail to notice the difference.

Thanks for the responses. It's more a psychological issue than a practical one; I even have time to fix the thesis itself. pm133, by "cheat" I only meant it was in the same field I used to work in, so I'm very comfortable with the data collection/interpretation and the analysis needed. It is not based on actual work I previously did.

So yep, you have no problem, just fix it. That's what I did, but these were only minor errors I made in writing the thesis.

Everyone makes mistakes. Do what you can to put it right if there is anything, and then when you've done that put it behind you.