This happens to me and my HW is mostly the same. The problem occurs with 2.6.32 and KMS enabled. When X starts then some glitches appears in the screen in both X server and TTYs.
With 2.6.31 or less it only shows a black screen when X starts, and the system input locks. The following errors are displayed to output: .../../../libdrm/intel/intel_bufmgr_gem.c:825: Error setting to CPU domain 91: Input/output error .../../../libdrm/intel/intel_bufmgr_gem.c:899: Error setting domain 72: Input/output error It is related with dbug #558237, but X starts with screen corruption.
