MDAC 2.7 intermittant connection faulure

I am still experiencing an intermittent connection failure on application
start up under XP.

My application now connects on creation of the main form to both an Access
97 mdb and an Access 200 mdb file using Jet 4.0 data provider.  Under Win9x
and Win2k, i.e. older versions of MDAC, all is well. But under XP (with MDAC
2.7)  sometimes on setting connected = true get error:

Cannot open database ''. It may not be a database that your application
recognises, or the file may be corrupt.

Now the Jet OLEDB:Engine Type is set in the connection string, a previous
reply suggested this might help. I was hopeful too :((

When I only used one mdb file this was the one that connection failed on
(and retrying would succeed). Now I have two mdb files (with no link between
them), it is the connection to the second one (in Access 2000 format) that
gives the intermittent failure. This also sometimes throws up a "permissions
failure" error message instead. Crazy as the permissions remain constant -
it is a static single user  DB.

So again what is happening here? Any ideas?? Why would connection sometimes
fail under XP or MDAC 2.7? Could there be some kind of timing issue?

Any ideas welcome.

Dave

D5, DiamondADO onto Access 97 & 2k mdb file using Jet 4.0 data provider