Can't boot iMac REVB after install


I have a RevB iMac with 160MB RAM and a maxtor 40gig hd with 4 partitions. I have installed DP3 with no problems, didn;t try DP4. Just installed X beta to the 4th partition and after the reboot it just stays at a grey screen. Does NOTHING :(
The only way for me to get out of this screen is to zap the pram then it boot back to OS9
Anyone else have this problem???? If so, how did you fix it?
This is just a suggestion, and it probably won't work. But I would try wiping out DP3. That might be causing some type of conflict with the Public Beta.