If it fails memtest, RAM is no good. Period. I've seen ram catch on fire before. Pretty site, but god awful smell.
At least you know the memory is fucked. I spent about 2-3 days trying to fix an "overheating PC" that kept giving segmentation faults when I compiled source... never rebooted, never cocked up in any other way. Simply would not compile with any level of consistency. Memtest ran for 16 hours without error. Finally pissed off, I swapped the RAM. Problem solved.
Apparently not: http://forums.gentoo.org/viewtopic-p-5032949.html#5032949 Had that guy not posted, I would've waited even longer to try new memory.
Memory tests can take forever to run properly. There's no substitute for sticking a new stick in and seeing if the problem goes away!
Actually the chances of finding an error in pass 2+ are many fold lower than finding one in pass 1. You'd think 16 hours of memtest would mean I could compile for more than 5 minutes. Yet, there I was.
You know what else is fun? When your fucking PC starts BSODing for no reason, so you run memtest for a day, get no errors, run it again for 5 seconds and get 3 errors. Then you buy new RAM, stick that in, a day later you BSOD like crazy, get no memtest errors, throw your old sticks back in, and suddenly your computer works fucking perfect. I just love whatever ghost pokemon haunts my electronics.
