Having massive issues with low frame rate. Not sure what to do.

Can anyone explain to me why my FPS in LOTRO will sometimes bounce from 1-25 fps, but on average be around 20-25? It gets worse when I get near a town. The kicker is the game detects my optimal settings at Very High but even if I put the graphics on VERY LOW, NOTHING changes. The FPS is the same. Anyone have any clue as to what is causing this? The computer will also shut off completely with LOTRO running if I have anything else open. Doesn't happen all the time but it will do it. I just preordered Helm's Deep and I think this issue is getting worse. I really need some help with this if anyone could give me advice that would be great. I've tried different resolutions etc. but nothing really phases it.

Here are my specs:

Intel Core Quad Core Q8300 2.5 GHZ
GeForce GTX 570
6GB of RAM
64bit