If you have a multimeter you could test to make sure you are getting power to the mirror. Sounds like a fuse to me. but I looked it up at:
http://www.qualitycareservice.com/default.asp?page=E4and I couldn't find a fuse or relay for them.
May be printed on the cover to the fuse panel and the PDB in the enigne comparment. You will need to make sure there is not more than one fuse or relay. Probably blew something because the motors were overheated when the mirrors were frozen.
If not the case, you can test the wires on both mirrors to make sure you are getting power. You could also test it at the switch to make sure you are getting power there.
Hope it helps.
If the mirror doesn't move it could be the motor is bad. Does the motor in that particular mirror make any noise when you try to adjust it? Sometimes my passenger mirror will stick when I try to move it, but I can hear the motor trying to work. Usually this only happens when it's extremely cold though, like now. After a few attempts, it breaks free and moves about like normal. 