Ok i had this problem with Beta 24 after all previous betas had worked fine.
Dumped out with same messgae everytime.
My cure was to lower the resolution, i have always run AH2 at 1600 res but by lowering selection to 1280 i got in straight away.
Tried selecting back to 1600 and got dumped again, tracked it down for some reason to monitor hertz setting.
With previous beta i could run monitor at 85 hertz, with b24 it will not run unless i drop the hertz to 75.
At this setting 1600 x 1200 res works fine again.