[AccessD] Microsoft Jet Database Engine could not open the file - Error

Hi Folks,

I think I have a versioning problem here but would like to get others
inputs before spending a lot of time going down the wrong path and/or
driving the 50 miles to visit the client site.  I have a client with a
small peer to peer network.  We have an Access 2000 front end/back end
database on their system.  The machine with the back end on it is
running Windows XP. The other two machines with front ends on them are
running Windows 98.  There is also a front end on the XP machine.  The
database runs great on the XP machine.  The front end/backend were
linked using UNC paths on the XP machine.  The front end was then copied
over to the Win98 machines.  On opening the remote front ends there was
an error. In going through the various obvious debugging options I had
them try to open the back end directly from Access on the client
machine; we get an error message: "Microsoft Jet Database Engine could
not open the file "dbUNCPath\dbName.MDB"  It is already opened
exclusively by another user, or you need permission to view its data."
Access security is not set on the system and we looked at folder and
file permissions and that does not seem to be the cause.  

I am wondering if this could be a jet issue.  Would different versions
of Jet on the machines cause this type of error?

Any inputs are greatly appreciated.

Doug