Abit BH6: CPU is unworkable - WHY??

I have a ABIT BH6 mobo with a Celeron 300A (slot 1).
Now i have installet a Celeron 466 (socket (370 i guess)) which is placed on a Socket-to-slot1 converter which I have used on a Asus mobo for a year or more.

First when I boot it tells me that it has a Celeron-MMX 432Mhz. but a little later during boot it stops with the message: 'CPU is unworkable or has been changed (Recheck softbios)'. If I press F1 it does continue but is unstable.

When I look in the softbios it has the setting '233 (66MhZ)'
meaning off course CPU: 233 and FSB: 66.
Now I have upgraded my bios to the latest version from Abit and it should support socket versions of Celeron up to 600MhZ.

When I change the speed to 466 MhZ or whatever I have tried it tells me the same as first time 'CPU is unworkable....' and the sets the clock back to '233(66)'


What is wrong???
Please help.