time machine prefs excluding my boot drive

Running Lion.

In 10.6 I had Time Machine backing up my Boot Drive to an external drive.

In Lion I'm trying to do the same but going to TM options I see that my Boot Drive is selected in the "exclude items from backup window". When I remove it and close the options screen, then reopening the options screen, my Boot Drive pops right back up in the "exclude" window.....hence I can't back up my Boot Drive because my BD is selected to be excluded.

Any thoughts?