I had a sort of similar problem, when I used an internet browser (Opera or FireFox). Basically, whenever I was surfing the net, the whole system would crash, and I couldn't even open a the terminal with Cntrl + Alt + F1. So , this is what I did, and managed to solve it.
Well, since I use UbuntuStudio (special Ubuntu distro geared towards those who use Music and Video Technology programs), I rebooted but with the RealTime Kernel selected in Grub. Since I haven't been having any problems since, I figured that the new kernel that came with 10.4 must have caused the problem.
I can't really remember how I downloaded and installed the RealTime Kernel, but I'm sure you'll find comprehensive instructions if you run a search for it.
Hope this helps, let me know how it goes.