About a month and a half ago, I went to close iTunes and it wouldn't quit properly. It got stuck in the dock and nothing could make it quit. The same thing then happened to Finder and iCal. Activity Monitor wouldn't open properly and Terminal couldn't find the process names. So I did a hard reboot (because it wouldn't work any other way) and thought it was just a one-off glitch. It happened again and again with different programs each time. So when I got back from a trip at the end of August, I decided to reinstall Mac OS X (Erase and Install). Thinking that I just had a corrupted system file or something I expected the problem to go away. Unfortunately, it happened again just as I had got my programs reinstalled and my documents back in place. I checked that the RAM was seated correctly and found that one RAM slot had some damage and I couldn't get the RAM back in. So I decided that it was time to call Apple. That was my 4GB of RAM I got from Crucial BTW, as I was giving Apple a call I put the original 1GB back (or to be more accurate the 512MB DIMM) because I heard they don't work with your own upgrade. They arranged for my MB to be picked up and repaired. Last week the repair place phoned to say that they couldn't find anything wrong with the computer and wanted me to explain. I said about the RAM (that I had included with the computer in a static-proof bag) and the technician was able to get it back in, saying that the damage to the slot was just cosmetic. He said it could possibly be Boot Camp not being removed when I reinstalled Mac OS X or something else wrong with the HDD, so he suggested a new HDD. Today I got the computer back and there was a new password (which I wasn't told about) so I figured I'd reformat it (again!) so that I could remove some of the included stuff as well. So I did all that and I copied my documents and apps back onto the computer (this time making sure to copy as little as possible to eliminate any corrupt data). It seemed to work fine for a few hours, then I went to empty the trash and the problem happened. Finder crashed and wouldn't relaunch, Activity Monitor froze for about 20 seconds on open and then showed that Finder wasn't running. I tried to open Finder again, and got the message in the attached screenshot. So I started Safari to make a post similar to this, when I tried uploading the attachment Safari died. I restarted the computer and left it a few hours before coming to post this. So in summary: OS Reinstalled Different RAM New HDD All didn't work. I don't use any particularly abnormal 3rd party apps (certainly none that modify system files). Before it started, I hadn't changed anything (no new apps or hardware for months) - the only new thing I can think of is MobileMe. I did have iDisk crash the Finder a few times, so it could be that. I realise this post is becoming really huge, so I'll end. Does anyone have an idea what would be the best way to go? Call Apple/repair centre again? Wait for 10.5.5? I really need the computer for University in a few weeks and I just can't trust it. Nor can I cope with multiple reinstalls (of Mac OS X and Windows) - which so far have been pointless. I had seen some people with the -600 error, but that seemed to be due to some parental control app which I wouldn't install.