Windows backup utility hangs on Windows 2003 SP2

[Suraj Wellala]

Our company has a HP ML350 G4p server with windows 2003 Ent. Sp2 installed. The backup system we use is on tape (HP DAT72). Up until few months ago the backup was running perfectly. However suddenly it stopped working.
When we start back to tape, the entire server hangs from that point onward. Then no services could be accessible via network. No even echo pings. This is very strange and we need to force restart the server to make use of the services again. Eventlog does not contain any useful information.
The backup procedure for our server is Sunday full backup and daily incremental backup to the hard disk. On Friday we backup all data to tapes manually.
Backup reports contained following two error reports
Backup Status
Operation: Backup
Active backup destination: File
Media name: "NTLK02.bkf created 18.Aug.2009 at 7:17 PM"

Volume shadow copy creation: Attempt 1.
Timeout before function completed

Error returned while creating the volume shadow copy:0x80042319.

Error returned while creating the volume shadow copy:80042319
Aborting Backup.

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The operation did not successfully complete.


Friday interactive backup:

Cannot locate the specified media or backup device. This backup operation will terminate.

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Does any have experienced such a situation like this and could help me to resolve this? Thanks