Finally got Republic Commando working. After - on the suggestions of Activision support (which is apparently staffed entirely by Scotsmen) - upgrading my video drivers, re-installing my sound drivers, shutting off the second monitor, dropping down to 4x AGP, fixing the refresh rate at 60Hz and downgrading my videos drivers to the version between the one I had before I upgraded to the latest, I spotted that the video display window was what was crashing. After I'd uninstalled some dodgy Matroska codec I'd used to try and play some clip someone had uploaded of the Daily Show it worked.