Next thing to look at is the GPU registers. Please install xserver-xorg-video-intel-dbg and run the tool intel_reg_dumper once when the screen is working correctly, and once with it showing the blank screen / out-of-range error, and attach both files. Comparing the register settings for them may highlight where the problem is.
Hrm, ok at least it rules out ia32-libs.
Next thing to look at is the GPU registers. Please install xserver- xorg-video- intel-dbg and run the tool intel_reg_dumper once when the screen is working correctly, and once with it showing the blank screen / out-of-range error, and attach both files. Comparing the register settings for them may highlight where the problem is.