In some cases, the geometry may not line up perfectly, which can cause what is known as "Z-Fighting", which appears as texture flickering in the game world.
In some cases, the issue may be remedied, or at least minimized, by updating your graphics card to the most recent drivers. The Drivers for ATI and Nvidia cards can be found at the following:
Nvidia:
http://www.geforce.com/drivers
ATI: