Very similar problem.
My Compaq EVO 110 laptop was rock solid with Breesy. With Dapper it locks up randomly when I use Firefox. No mouse, no keyboard, no any massage. I use ATI Radeon Mobility and the ATI prop. driver. I use the latest upgrade, but this bug persists from the beginning. I have tried both 386 and 686 kernel, open and propr. drivers. No change.
I have no idea what to try yet.