Eric,

Over on the server, what do you see as output for QUERY FILESPACE
<name-of-this-client>.  Are any of the filespace names for this client in
uppercase?  Mixed case?  Do you see a filespace named '\\spln68037\c$'?
Filespace names are case sensitive to the server; the strange thing is that
when the backup starts, the two messages present the names in different
case, and it is the lowercase name which is reporting not to be known to the
server.

P.S. What's the client and server version?

John Sorensen
SSSI