Or a short in the dryer caused the breaker to trip.
If resetting the breaker restores the voltage, put a 120v 10A hair dryer from the ground terminal to one side of the line, then the other, so the hair dryer sees only 120v each time.
If the voltage to the hair dryer rises substantially more than ~1v [e.g., from 119vac to 120vac] when the hair dryer is switched off you have a bad connection.
Test both lines. If the hair dryer fan doesn't run, turn it off immediately; you have found your problem.
If the power source passes this test, almost certainly the dryer has a problem. Much less likely, both have a problem.
Last edited by Yoyizit; 11-19-2009 at 05:04 PM.