Hi.. I have a few users syncing to ACT 6.0 successfully.
All ACT users have a User Name and but all have a password. If your boss doesn't have to enter a password when opening ACT, then you should just have to type his User Name in. Look in ACT, in File, Maintenance, Users (or something like that) and see what his name is entered as in the list of users. That should be the User Name and the Blackberry desktop software is looking for.
ACT should be closed when trying to sync as well.
I have one user with a large ACT database on ACT 2007 (like 6000 records). I used the CompanionLink software and it works better then BB Desktop. It's only $50 so not too bad either. Might want to check that out. CompanionLink -- AddOnStore for ACT!
BBs are way easy to sync to anything... Try a Treo! That's hard.
Let me know how far you get.