If a player runs out of time and their opponent has insufficient material to checkmate, then the result is a draw.
Your opponent had only a king. How could he have possibly checkmated you? You must have run out of time while you were trying to straighten out your computer.
I recently played a game on Live Chess that I was very close to winning. My browser froze and got buggy for a minute (as it often does because my computer sucks), and when it straightened out the game had been "Drawn by Insufficient Material." My opponent was down to just his king, but I still had a queen and two pawns, one of which was one square away from promoting. I thought insufficient material meant that checkmate could not be forced with the remaining pieces? Clearly I was still able to do so, so am I misinformed somewhere? Also, the last move was 1.) Kd3. There was no change in material on that move. Something is screwy here, right? Here's the final position: