In a post last week, I complained that one of my Rainbow installations was hung on the update screen with the 'Your Database is up to date' message.  I found a solution (work-around, really), but more explanation is in order first. 

I had backed up a production database onto a local server, then tried running the update.  This backup had been made by copying the production data over an existing database, with the data copy mode set to 'overwrite'.  This is the scenario that caused problems. 

I ended up wiping out all tables in the local database, then running the data transfer again from the production site to the local one.  When I ran the update against this new local DB, it went just fine. 

So, I solved the problem...but I don't really know what it was...or something like that.