Left transmission running over night and the charger wasn't plugged into the socket properly. Woke up this morning to a drained phone. Plugged it into the charger and it showed the Nokia logo. Tried turning it on 20 minutes later and it wouldn't turn on. Left it off and charging all day. Came home, took out the battery, waited 2 minutes, held down the power button on the N900 for about 20 seconds. Plugged in the battery and it turned on just great.

Thanks for the solution.