On at least a dozen occasions, I've spent 2-3 hours figuring out how to get Ubuntu 11.10-12.10 to either update or acquire software from software center, or both. I want to fix whatever is causing the BADSIG problem once and for all; I've wasted so much time trying to get this to work well enough that I can rely on it, but the same problem comes back after a couple weeks of normal updates and software center usage.
Don't refer me to a standard posted solution on the web---whatever it is, I've used it more times than you have. The question isn't whether I can get it to work right this afternoon. I can. The question is what is causing the problem to recur regularly across 3 releases.
Notice: I use this computer 4-5 hours per week and I do little on it. PDFs, Latex, FireFox, Mendeley, and that's it. I don't constantly install new software, and I don't fiddle with things unnecessarily.