The "check your bathroom GFI's" is a good tip. Lots of tract homes were built and ran the garage outlets off of one of the bathroom GFI circuits in order to save $10 on installing a separate GFI in the garage. Now Most codes prohibit bathroom outlet circuits from serving other rooms with only a few exceptions.
You might check to see if you have any OUTDOOR receptacles that have a GFI breaker in them. It's possible that the circuit you are having trouble with is wired to an outdoor outlet that's the GFI outlet, then to the ones that you are having trouble with. Have you recently plugged something into an outdoor outlet? It's also possible that there is a GFI outlet somewhere in the garage that is behind some large cabinet, freezer, whatever, that tripped. Lastly, it's still possible that you have a loose connection inside one of the outlet boxes. I've found this issue in my home. The problem was found inside one of the outlets that was WORKING. Power was "daisy chained" at the outlet and the power going out was a loose connection. so keep in mind the problem could be located in an outlet box that is still working.