Comment 5 for bug 118225

It looks like the same root cause. The misdetection in 3731 _usually_ just reduces the number of available resolutions to one or two for most people, but it is possible in some rare cases (such as yours) for it to reduce the number to zero.

I believe that the crash is due to it finding no resolutions.

However, normally 3731 is resolved by manually adding VertRefresh and HorizSync, so since that isn't working in your case, I'll de-dupe it. Possibly this has been reported upstream to xorg already...

Did you try moving aside the xorg.conf and restarting X?