freeze up ?
you need to give more info.
error messages ?
mouse still respond ?
can you re-start X with ctrl-alt-backspace ?
anyway, it sounds to me like its the graphics drivers / openGL.
are you running a clean fedora install ?
if so, install the ATI graphics card driver, it will be much better that the generic one that comes with linux.
also, you need a subject title. most people
decide wether or not to read a post depending on its title.
every1 who posts wants help. you dnt need to say that.
but maybe put in your graphics card, and a brief description of problem.