Trouble restoring SQL database

[Champ, Ken]

I am trying to restore a SQL database and am having trouble with the
Diff restore. I can restore the full backup but when I try the diff I
get an error that says:
[Microsoft][ODBC SQL Server Driver][SQL Server]Cannot apply the backup
on device 'TDPSQL-00000798-0000' to database 'Core'.
[Microsoft][ODBC SQL Server Driver][SQL Server]RESTORE DATABASE is
terminating abnormally. Has anyone had this problem? Any ideas?
 
thanks,
Ken Champ
USA Datanet