Never heard of that. I could picture a scenario where a piece of dirt got in between the metal contacts causing a problem, but you could easily inspect the pedal for that yourself.

Just unscrew the the screws on the underside of the pedal, and with a pair of pliers, pull the springs out, releasing them so the pedal comes apart. You'll see how the momentary pedal works as soon as you take the thing apart. Basically it pushes a raised metal bump down on the green board, which makes the connection on the circuit so that the motor goes.

That metal button may be damaged, cracked, or - like this person is suggesting to you, it may have a piece of dirt under it. I would bet you anything that the button is damaged in some way though. The last time my pedal broke this is what it looked like:

http://www.calfishing.com/dc/user_files/4802-foot_pedal_zoom.jpg

Once the covering over the button got cracked, water got in to the board and shorted it out. It's a crap design on Minn Kota's part and a big reason why people are always complaining that their foot pedals are broken. This might sound stupid, but try spraying WD-40 on the button if it's cracked. That brought mine back to life for a while.