Hello,
A number of users have reported that VLC systematically crashes while trying to play a video on Ubuntu. This is a known issue in the ATI display driver on Ubuntu side, and Canonical is working on it. You can find more details in this bug report: https://bugs.launchpad.net/ubuntu/+sour ... bug/921384
In the mean time, I can only recommend that you keep off Ubuntu 12.04 if you have an ATI card until the problem is resolved.
If you really want to upgrade to beta versions of Precise, then you should explicitly select a different video output than XVideo in the VLC preferences: either GLX / OpenGL or X11. If you do that, know that VLC will be slower.