...The first question I have what 3.1 roms are you using? You need ones that are for the 1200 (not 4000d or t)....
What? No you don't. You need the 3.1 ROM for the A500/A2000.
Since you have a revision 6A, the A500 3.1 ROM should just plug in fine with no modifications (rev. 3 & rev. 5 require some soldering).
Are you using an original WB 3.1 disk? Maybe it has already been configured with an improper display mode or monitor.
