Problems with Quicktime and Itunes (windows version)

[rat1ca]

Everytime I try to play a video in ITunes or Quicktime, the program crashes. I have the latest versions of both (Quicktime free not Pro). These could be videos my kids did with a camera or movie trailers downloaded from the ITunes store. They will play in other software, just not the 2 mentioned. Any ideas. BTW, I did uninstall and re-install both pieces of software. Thanks.