Same thing just happened on my '07 EXT. Mine is still under under warranty. They had it for 4 days trying to figure this one out. They replaced the unit that does the blowing (fan) and it still didn't work. I believe I heard them say something about there being 2 seperate units, one for the driver and one for the passenger. They replaced both of them i guess, but I wasn't really paying attention and didn't really care since it was under warranty.
Turned out to be a problem in the wiring harness itself up under the dash somewhere. (or so they claim) Works like a champ now.