Do you have Quicktime installed on your computer? If yes and you can't edit then you can pay for QuickTime Pro which should allow you to convert to convert the QuickTime files to another format.
Another option would be to try:
Handbrake or
MPEG Streamclip
Both are free.
I don't use Vegas so I can't advise on the program or what options might be available for importing QuickTime files.