Is the 3D menu enabled?
What happens when you create a new extrusion layer?
I have the 3d menu up, but everything is greyed out...
I can't create a new extrusion layer because the Repousse feature is greyed out and not selectable
If you have a document open and everything is grayed out -- then something is wrong with your video card that prevents the 3D features from working.
Check the Help -> System Info log to see what Photoshop knows about your video card and drivers.
Here is the top portion of my log down to the installed components section (x'd out the serial, just in case)
I don't see anything wrong here...
Memory available to Photoshop: 14689 MB
Memory used by Photoshop: 69 %
Image tile size: 128K
Image cache levels: 4
OpenGL Drawing: Enabled.
OpenGL Drawing Mode: Advanced
OpenGL Allow Normal Mode: True.
OpenGL Allow Advanced Mode: True.
OpenGL Crash File: Not Detected.
OpenGL Allow Old GPUs: Not Detected.
Video Card Vendor: NVIDIA Corporation
Video Card Renderer: GeForce 8800 GT/PCIe/SSE2
Display Bounds:= top: 0, left: -1280, bottom: 960, right: 0
Display Bounds:= top: 0, left: 0, bottom: 1024, right: 1280
Video Card Number: 1
Video Card: NVIDIA GeForce 8800 GT
Driver Version: 126.96.36.1997
Driver Date: 20121002000000.000000-000
Video Card Driver: nvd3dumx.dll,nvwgf2umx.dll,nvwgf2umx.dll,nvd3dum,nvwgf2um,nvwgf2um
Video Mode: 1280 x 1024 x 4294967296 colors
Video Card Caption: NVIDIA GeForce 8800 GT
Video Card Memory: 1024 MB
Serial number: xxxxxxxxxxxxxxx
Application folder: C:\Program Files\Adobe\Adobe Photoshop CS5 (64 Bit)\
Temporary file path: C:\Users\Aza\AppData\Local\Temp\
Photoshop scratch has async I/O enabled
H:\, 537.5G, 251.1G free
F:\, 1.82T, 604.9G free
Primary Plug-ins folder: C:\Program Files\Adobe\Adobe Photoshop CS5 (64 Bit)\Plug-ins\
Additional Plug-ins folder: not set
Make sure your document is RGB or Grayscale.