Probably the first thing you should do is make sure that the drivers for your graphics card are up to date. If Chimera continues to fail with up-to-date drivers, then run Chimera in "debug" mode and let us know what the output is. You might want to send that to
chimera-bugs@cgl.ucsf.edu rather than chimera-users. That will open a ticket in our bug database for your problem and will avoid having everyone on this list receiving the details of your problem -- which probably wouldn't interest them very much.