Well that didn't last unfortunately. It was 3 days on and now its 3 days off. Sure wish I understood what was happening.
If you're scanning Favorite lists you created yourself, you need to manually check them to make sure they're up to date. Favorite lists do not get updated when the master database in the scanner is updated, so if site data changed (control channels or what have you), it won't work on the Favorite list.
I have a 436 (and an HP1) and have to keep on top of the favorite lists, what with all the changes going on regularly right now. Once things are finished up and settled down, you may find that this kind of thing goes away, more or less.