Bill, I think that reverting to 10.6.7 is NOT the correct thing (at least for now) to fix your problem. However, if it comes to that, or for future reference for everyone else, it is trivial to do.
Have your TimeMachine backup. You won't need it unless something goes wrong.
Go to support.apple.com/downloads and search for the 10.6.7 combo update for client. (There are 4 versions of each OS update -- client and server, and upgrade and combo update. You want the client combo update.) Download it. It is big, this will take some time.
Stick your 10.6 install disk (mine is 10.6.3) into your computer, and restart holding down the C key. When it boots off of the CD, install the old 10.6 from the CD. This takes a couple of hours.
When it finishes, it will reboot. Log in to an account with Admin privs, and go to your 10.6.7 combo update, double-click, and install it.
In 10.6 apple changed the way that the install CD works. It looks on your disk and if there is already a version of 10.6 there it does the equivalent of archive and install. If there is an older OS there, then it does the equivalent of an upgrade. The erase and install option -- which is almost never the right thing to do -- has been made a lot more difficult to get to. You have to go into DiskUtility and erase the disk, and then do the install after that.
You are done. The only thing that you have to do is to fiddle with Software Update each time it comes up, because it will continue to offer you the 10.6.8 update and so you will have to un-tick it.