When you booted up with new MB, did you wipe out your old Dev Mgr info? Sounds like a HW conflict.
If not U could try this, tho be careful, backup your system & registry first!
1)Copy WIN98 directory from your install CD to your HDD.
2)Go into regisrty, HKey_Local_Machine & delete the "Enum" key.
3)Re-boot, W98 will rebuild Dev Mgr using your current OS,MB,&setup.
4)You will have 2 re-boot a few times, your CDROM may not B accessable, refer windows to that WIN98 directory on your HDD...
Good Luck!