Issue with memory management on certain lines of cards. Use LOD Streaming and caching to help mitigate it. Depending on how congested an area is, it may help to turn of the HDR also...I know, it can make the skyline and some textures look pretty rough...but if it keeps you in game for hours instead of minutes, it may be worth the trade off until we get the DX11 client going--hopefully some of these texture issues will get addressed then.

Also, you may want to verify your cooling is up to snuff. Video cards can be a serious dust bunny magnet in some rigs. Had to constantly clean out the ATI cards that came with stock coolers--sometimes I replaced them JUST to get away from all the @#$@#$ lint balls. Also, if you've upgraded your GPU and you didn't already verify your Power Supply was sufficient, you may need to look into that as well. They provide less power when they get hot, and the longer you have them the more prone they are to have that capacity diminish over time.