I had terrible problems also. I was running 32 bit Win 7 (which I believe is what you are running). I wrote to turbine and received this..

"Thank you for your request. Please open the userpreferences file that is found in your Documents > The Lord of the Rings Online folder and within that file under the sectioned titled [Display] make the following changes:

Change AllowFakeFullScreen=True to False
Change SyncToRefresh=False to True
Verify that the number following Resolution= matches your current Windows desktop resolution
Change Antialiasing= to Disabled if set to 2x/4x etc. (e.g. Antialiasing=Disabled )
Change AllowDesktopCompositing=False to True
Under the section titled [Render] change the TextureDetail option to Medium (i.e. TextureDetail=Medium ).

Under the section titled [Troubleshooting] change the MaximumFrameRate option to 57 (i.e. MaximumFrameRate=57 ).

Exit the file and choose yes when prompted to save changes prior to launching the game to test these settings.

Some additional settings changes can be made from the in game Options menu (Note that after making these additional adjustments you will be asked to restart the game client once more so that it can save/apply these changes):

Under ADV Graphics disable the Player Mesh Combining setting.
Set Frill Distance to disabled.
Lower the Player Crowd Quality Control slider to 0.
Under Audio make sure that the selected sound playback setting is "Generic Software on..." and that Use EAX is disabled.
Under the Troubleshoot section lower the Engine Speed setting to Medium."

Although many of these changes degraded the appearance of the game, it solved the crashing. Rohan BTW is a lag fest and has been known for this since it came online. Can't wait to see what these massive battled in HD are going to be like (rolling eyes).