Crash...

I have installed AV on a new Windows 7 (64) machine and it updated fine. When I try and enable a scan, or run a manual scan it crashes the program. I get  the error message " Anti Virus has stopped working"

 

I have uninstalled and redownloaded and installed the program 3 times. It works on my other PC, running XP. And I have installed the specific 64 bit version for set up.

 

Any ideas?