If you're using XP or Win2k it should "just work". If you're using ME or 98 you may need drivers and may have trouble with USB Flash Card readers. I assume you're using XP.
Have you looked at the Canon web site? It says [link|http://www.usa.canon.com/consumer/controller?act=SuprtKnowledgeBaseAct&fcategoryid=221&modelid=12942|here] that if your computer locks up on connecting the camera, you should try a different USB port. If that doesn't help, browse around [link|http://www.usa.canon.com/consumer/controller?act=SupportDetailAct&fcategoryid=221&modelid=12942|here].
Since you have the same problem with the scanner, that's another indication that there's a problem with the USB port.
HTH a bit. Good luck.
Cheers,
Scott.