Hi, I've installed mint 10 KDE and it continues freezes. I think it is a problem with the graphics card, maybe the desktop effects...
I tried Kubuntu and the occurred the same problem after a short time working...
I tried booth systems with defaults apps to avoid that the problem is caused by an application error. Desktops effects came enabled by default, I only enabled cube desktop animation and some other simple window effect.
I don't know if it's a know bug??
The system freezes totally, neither ctrl+alt+f1 works, I have to shut it down with the power button.

TOSHIBA SATELLITE A505-S6981
4GB RAM
CORE 2 DUO 2.20GHZ
INTEL GMA 4500HD Graphics Card
Tested on mint 10 KDE and Kubuntu 101.10, 64-bits booth.

Thanks for helping!

Try this and see if it helps. Go to system settings->desktop effects->advanced and select XRender instead of OpenGL.
This will turn off a few effects. The end result should be a more responsive system.