Problems syncing rhythms between tracks.

I've just started using GarageBand 10.1. I've used the 6.0 version happily for years. The first two-track recording I made -- rhythm guitar plus lead -- was just fine. Then I downloaded some jazz rhythm loops from BetaMonkey. When I dragged one of them into a track in GarageBand -- each of the loops has its own metronome setting -- the drums and guitar tracks weren't in sync, although they sounded like they were when I was recording. Now even when I try to play two guitar tracks, they aren't in sync -- even though, again, they sound in sync in record mode. Not sure what i did. Can you help? Thanks. Jeff