Go to system properties and advanced system settings then where it says performance click on that and then on the Data Execution Prevention tab, make sure "turn on dep for all programs and services except those I select" is on and click on add which will then let you browse around, browse to the sony folder in the program files and find the vegas80.exe file and add that and apply, that's it. Start up Vegas and see what happens.
Found this online as well.
Do what it says but disinclude the "Sony Vegas" part and replace it with Cross Fire.