Don't think OS 10.1 can be correct ~ by chance do you mean 10.5.1?
If so update to 10.5.2 first up and then try the Graphics Update. If you are having problems do not use Software IUpdate but go to the Apple web site and download from there, run Repair Permissions, drag download to desktop from Download folder , disable antivirus, if any, disconnect everything but keyboard and mouse and install by double clicking.
Run Repair Permissions when finished. Any luck with that?