I have an USB Logitech mouse and a Microsoft PS/2 keyboard.
They never had a problem working together in mandrake and debian.
Recently I installed Gentoo for AMD64 on a new machine with same mouse and keyboard, no problem.
Then, I installed Gentoo for x86 on the same machine so I would be able to use ATI's drivers, there I have the problem. When using both the keyboard and the mouse simultaneously the mouse starts to jump over the screen clicking randomly. while this isn't very common in everyday use, I can't play games (like UT2004) this way (especially when holding the flak cannon
I tried switching between /dev/mouse /dev/psaux and /dev/input/mice Auto,PS/2,IMPS/2,ImPS/2 ...