Periodic lag experienced in graphics-intensive application

This lag is debilitating. So far I have only experienced it on the Windows 7 (64 bit) side of my Bootcamp partition, but I have not attempted to run such applications in the OSX side.

The Problem: About every 5.1 to 5.2 seconds, the framerate drops to a standstill. As this happens over and over again, the duration of the stutter increases until after about an hour it is equal parts smooth and lagged. Despite the increased duration, the periodicity remains between 5.1 and 5.2 seconds by my stopwatch. Eventually, the lag becomes so great that the applications become unusable.

I have found this problem in the following applications:

TERA Online

Guild Wars2

I have also found forum discussions citing the same symptoms in Diablo 3, although I have not played or installed that game on my own system.

This appears to be a common problem across all these graphics-intensive games specifically centered around the iMac. This is why I am bringing this up to the Apple community. Has anyone else seen this phenomenon? Is there a solution? I did just update the Radeon HD 4850 graphics drivers. Could that have something to do with it?