This works for me on the latest CrossOver Games (8.0.0) and on OS X 10.6.1.
The GOTY version of RTCW comes with two discs. This appears to cause a problem with the CrossOver Games unsupported installation. The simple solution is to ignore the crash notice - try to install the game as normal (insert the first disc), and when it asks you for the second disc, press the eject key on your keyboard. On Snow Leopard, you'll be given to force eject - do this. (On Leopard, you won't be given that option within the GUI; you'll have to use the Terminal and umount -f the CD drive.) When you force eject, the music will stop and you'll get a message that the application crashed. Ignore this - it worked fine. The box asking you to insert the second CD will still be open, and so insert the second CD. Press OK, and it'll work fine! Do the same when you're asked again for the first CD. At the end, the installer will give you an error, but the resulting installation seems to work fine.