I've had the same issues. Yesterday I found the solution for my problem (display going black after few minutes, while audio is still playing):
- Run winecfg
- switch to the Graphics-tab
- in the section Direct3D: disable the support for Vertex Shader (choose "off" in the dropdown-box)
- in the section Direct3D: check the option "activate Pixal Shader"
- click OK and you should be good
Also, I have set the VideoMemorySize in the Registry as suggested by others here in the forum. (but that did not solve the problem for me)
I have a german system, the texts above might differ slightly.
My Mac (I do own several Apple Macintoshes, but use this one mainly for gaming and running Mac OS X out of curiosity):
Hackintosh Quadcore CPU
8GB of RAM
Nvidia GeForce 8800 GTS (640 MB)
Snow Leopard 10.6.2
CrossOver Games 8.1.4
LotRO running in a virtual desktop at the display size 1600 x 900 (fullscreen)