Error 3241on transaction file backup

Hello,
I am starting to get the following error message when a transaction backup
is scheduled to run:

Microsoft (R) SQLMaint Utility (Unicode), Version Logged on to SQL Server
'MAIN' as  'MAIN1\Administrator
' (trusted)
Starting maintenance plan 'TEST Maintenance Plan' on 5/31/2005 10:33:43 AM
[1] Database TEST: Transaction Log Backup...
Destination: & #91;D:\Backup\TEST\T
 EST_tlog_20050531103
3.TRN]
[Microsoft SQL-DMO (ODBC SQLState: 42000)] Error 3241: [Microsoft]&#
91;ODBC SQL
Server Driver][SQL Server]The media family on device
 'D:\Backup\TEST\TEST
_tlog_200505311033.TRN' is incorrectly formed. SQL
Server cannot process this media family.
[Microsoft][ODBC SQL Server Driver][SQL Server]BACKUP LOG is ter
minating
abnormally.

I have plenty of room on the D Drive and SQL 2000 is at the SP3 level.  This
transaction (TRN) backup job as been running fine until recently.  The
regular backup (BAK) runs fine.  This error occurs when the backup is
scheduled to run or manually run from query analyzer.  The only KB I found
is 297104 and it states the the problem was fixed in SP1.  The problem
exists with this database only.  Other databases in the scheduled backup run
fine.  Is there a size limit to transaction file backups?  The size of this
database is about 3GB.

Thanks,
Joe