I could not find any other threads about this so here's a heads up. Something went horribly wrong with the reltionship between QB13, FMBooks Connector, and FileMaker. My understanding is that it was the most recent QB (b6) update. My understanding may be wrong, but the point is don't upgrade quickbooks or you may (WILL) lose your connection between QB and FM.
Productive Computing is very aware of the situation, and they are working on a solution. In the mean time everyone we know of with the FMBooks Connect 5 and QB 13 are "dead in the water".
This all happened on Friday--which is such a "good" day to take down a financial system.
If anyone finds a work-around or solution. Please share.