Is now something like 2 weeks since my system gets frozen while browsing the web, using apps, watching videos on web sites, basically using any part of my netbook, even when i'm only using one program (like the web browser) this happens. Is so frozen, that the only option i have left to do is to PRESS and hold the power button, nothing else works; I have seeing an error message telling me about a "compiz" error, but not all the times, and this happens every day, some times 2 or 3 times, during the same day. Why does this happens? how can i fix it? please help.

Just to let you know i have my system up to date on 12.04 32 bits version, working on an Acer aspire AOD257, 1 Gb RAM, Intel® Atom™ CPU N570 @ 1.66GHz × 4 .