After the update my game would freeze every 5 seconds or so making it unplayable.
Then i remember that i had recently enabled the Catalyst AI, so i disabled it and the problem went away.....
About 30 minutes later it returned, so i opened up the task manager and the Defense Grid CPU usage was all over the place, constantly jumping from high to low etc
So i set the Affinity to one CPU ... problem solved, for me anyway
I don't think the recent update likes multiple cores.
Phenom II X4 940, 8gb, 4870x2 (10.2), Win7 x64 - running DG at 1074x768, High, Windowed.