When ever my Cache memory gets extremely high, my entire computer slows down. Windows slow to load, and there's lagging on the mouse-overs for everything. The only way I can restore everything is by rebooting. This happens particularly whenever I view a youtube or any video in fullscreen. The Cache memory goes up, and the computer slows. It has just happened again after making a virtual box vdi file. After creating a blank vdi file, the computer is really slow.
I don't think virtual machine usage has anything to do with it, since it happens even when I haven't loaded any virtual machines.
It happens mostly when I watch a video in full screen. Next time it happens, I'll try to see what more information I can find in the system monitor.
I use the fglrx driver for my ATI Radeon 5000 series graphics card, but I'm unsure if this is a driver issue. This occurred in Ubuntu 10.04, so I installed Ubuntu 11.10 (removing 10.04) thinking it would solve the problem, but it hasn't.