I had a problem with this (access violation and stuff). Googled around and found some pointers. It could be iTunes and/or QuickTime. I reinstalled the latest. But I kept having some problem with my video editor (Magix) with mov and avi files amongst others. Perhaps divx related. Anyway, I reinstalled divx6. I noticed some qt files being installed (qt is QuickTime is Mov, so that makes sense). Now everything works as normal. Problem solved.