I've had mice do that too, I always thought that it meant that they were nervous and maybe looking for a fight. Whats really odd is sometimes I get 'flying mice'.. They POP out of the tubs as soon as I open them with all 4 legs completely outstretched and their tails waggling around like crazy. It's like they're gliding and using their tails as a rudder. They're off like a shot as soon as they hit the ground and are harder then heck to catch.