> Can anyone suggest any other avenues of attack? We are now
> operating without a net - our last good backup was Thursday
> morning...

You could try:
http://www.telesiscomputing.com.au/dbk.htm

This may let you rebuild your database before reverting back
to gbak (if you want). DBak is slower than gbak so for an
18Gb database it will take a while.

--
Geoff Worboys
Telesis Computing