Debugger problems

I'm not able to get the debugger working in PCSX 0.8.1 (devel and release versions). I've dumped Disgaea (US) to an ISO and it runs fine when I use Run/Execute, but when I close the display window and hit Debug/Enter Debugger, it always displays the PC as 105fb0, no matter what point I'm at in the game. I try to use the Step button, but nothing changes when I click it. When I click Go, the display freezes and PCSX pegs the CPU at 100% until I eventually kill it. While it's sitting, it doesn't output anything to the console.

My goal is disassembling the checksum routine for saved games, so what I want is to escape from the running game and single-step while that's happening. Is there something different I should be doing to get the debugger to work?