ah so we found the culprit then, compiz is great but still has a few kinks that need to be worked out sadly.
Thing is it's eye candy but at the moment there are other things that needs to be fixed in any form of linux before we can start adding eye candy, don't get me worng it's nice to have but we need to add more support for some types of hardware make the display devices more tuneable before we add junk.
I know it sounds mad coming from me but honestly linux lag's behind in display customisation compared to Windows and OSX, that's a shame and it needs to be fixed soon.
I am a huge fan of Linux but I find it's monitor configuration set up abysmal that needs work before it can truly considered a non techie desktop OS.