I have a similar problem with my Voodoo 5500 PCI and my Mediator 1200 (ok... it's an Amiga 1200, and not 3000).
My problem is that sometimes the busboard recognize the card and others not.
Elbox told it's an HW problem of the Mediator itself, and only with the Voodoo 5500 (now I cannot remember why). It could be that your busobard have similar problems...
To solve the problem of the plug I suggest you to try to mount the card in a PCI slot of a standard PC and see how it plugs! If it's ok, could be that the problem is the Mediator...
