You ran out of time. Instead of losing, you got a draw because your opponent has insufficient material to checkmate you. You don't get a win, because you have insufficient time on your clock (maybe they should change the message )
Game Error - Insufficent material on pawns turned rooks!


- The side that had the two rooks ran out of time.
- Normally if you run out of time, you automatically lose to your opponent.
- But the opponent only had a king and so could not possibly have a winning position.
- Therefore it was declared a draw because the only side that had time remaining did not have sufficient material to win.
EDIT: I was beaten to the punch... oh well.
This image basically shows the problem (note it says insufficent material for me, white, and I have two rooks and a king).
Note 2: Both of those rooks came from pawns if that helps (It may be a problem there).
http://i51.tinypic.com/2vbv8lx.jpg