Chris,
I don't know if you managed to get this issue fixed for your father but if it is still a problem here is the fix. Mainly because I am using nearly the same configuration as your dad except that I couldn't get 11 to fire up after installing Norton 360 v3.0 (v2.0 worked wonderfully).
If you contact Norton support from inside 360 and get a Norton tech support person and tell them that there is a program that will not start up after installing 360 they will install some sort of a "Hot Fix" that deals with an issue that prevents ceratin programs from starting up with 360.
After this was installed Vectorworks went on to run like a champ again (after a reboot of course).
Good Luck!