Sorry to hear that, Fritz. If AVG simply won't let you keep your LB2.EXE all I can suggest is changing your AV program and trying. I have had no problems with AVG but a lot of people have switched to MS Security Essentials - Microsoft's free AV program. I have that as well and it seems to be good.
That's not to say that you won't run into problems with the game itself though, after you've actually got it to load.