No address conflict, but locks anyway?
If you happen to use a motherboard with non-standard or incomplete PCI support, you could try to shuffle the boards a bit. I am running an ASUS TP4XE that has that non-standard modified “Media Slot”, i.e. PCI slot4 with additional connector for ASUS-manufactured SCSI/Sound combo boards, and I experienced severe problems while running a Diamond Monster 3D in that slot. The system operates flawlessly since I put the board in one of the regular slots.