--- Operating System, Graphics card ---
Ubuntu 12.10 amd64
NVIDIA GeForce GTS 450
Video driver: 304.51

--- Blender version with error, and version that worked ---
Version with error: 2.66 Testbuild1 (2.65.10 r54336) x86_64
Version that worked: 2.64a (2.64.0 r51232) x86_64

Also tested official 2.65a (2.65.0 r53177) and 2.65.9 r54314: bug present.

--- Short description of error ---

With VBOs enabled, when adding multires modifier before entering sculpt mode and then subdividing, faces of the mesh are painted with random colors. This behavior seems inconsistent: in one of my tests default cube just disappeared. Leaving and re-entering sculpt mode or subdiving further gets rid of random colors.
With VBOs disabled the bug does not occur.
If Multires modifier is added after entering sculpt mode and "subdivide" is clicked, bug does not occur.

--- Steps for others to reproduce the error ---

1. Make sure VBOs are enabled
2. Load default scene
3. (Optional) Add and apply level 2 or 3 Subdivision Surface to default cube (to better see random coloring)
4. Add Multiresolution modifier
5. Enter Sculpt mode
6. Hit Subdivide in Multiresolution modifier panel