Once...and it was a pretty scary one. Heading out of BOS during a very, very cold night heading home for Thanksgiving I think. I think BOS was down to one or two runways b/c of winds....etc...so we head to power up as we were turning onto the runway. As we powerup we continue going straight...the plane doesn't turn...and we almost go off the runway...at the last second, the aircraft turns...and then does a few strange turns going down the runway...but not accelerating. Apparently, our front landing gear had frozen, and we had trouble turning. So we went back to the Penalty box...waited to be de-iced. Then went to near the gate....waited to be de-iced. Finally were de-iced, checked if the gear worked (by making sharp turns down a taxi-way) and took off about 3 hrs late with lots of scared pax...and scared flight attendants, 2 of whom mentioned they wanted off the plane. To make matters worse, it was a late flight, so lots of people had already missed connections in ORD, and wanted to stay in BOS that night...however, no one had the opportunity to get off. Lots of angry, somewhat scared pax.

-W