Updates to Defense Grid have been released. The updates will be applied automatically when your Steam client is restarted. The specific changes include:
Defense Grid: The Awakening
Fixed a rare problem in which some systems would play the game and see a solid color instead of the level.
Made the Siege Breaker achievement obtainable.
Corrected the accumulation of the stats: Spires Encountered and Total Aliens Encountered.
Adjusted the in game resource counter to allow for 7 digits instead of 6.
Corrected a bug dealing with the accumulation of interest when using checkpoints or saving/loading near the end of a level.