Backup exec fail every time I backup Shadow copy, system states or exchange

HI! I get a failed backup every time I backu a shadow copy component, sytem state and/or exchange DB on a local or remote server. If I backup only files I get a success backup status.

Backup Exec is version 11d rev 6235 Service Pack 3, Hotfix 35, 38 and 39.

I also installed WindowsServer2003-KB940349-v3-x86-ENU.exe on the Backup Exec server.

Job monitor status:
Full Backup -- The job failed with the following error: A failure occurred accessing the SnapShot handle.

Alerts:
Job ended: May 12, 2009 at 9:59:06 AM
Completed status: Failed
Final error: 0xe000fec2 - A failure occurred accessing the SnapShot handle.
Final error category: Resource Errors
For additional information regarding this error refer to link V-79-57344-65218

I get this alert every 15 minutes:
Please remove media from the drive.

Job Log:
Errors:
Backup- \\DC01\Microsoft Information Store\First Storage Group V-79-57344-65218 - A failure occurred accessing the SnapShot handle.
V-79-57344-65218 - A failure occurred accessing the SnapShot handle.

Exeptions:
Backup- dc01.prudent.localV-79-57344-34110 - AOFO: Initialization failure on: "\\dc01.prudent.local\Microsoft Information Store\First Storage Group". Advanced Open File Option used: No.
The network connection failed during the snapshot. Check the network, and then run the job again.

Backup- DC01V-79-57344-34110 - AOFO: Initialization failure on: "\\DC01\Microsoft Information Store\First Storage Group". Advanced Open File Option used: No.
The network connection failed during the snapshot. Check the network, and then run the job again.

Backup- \\DC01\Microsoft Information Store\First Storage Group V-79-57344-34110 - AOFO: Initialization failure on: "\\DC01\Shadow?Copy?Components". Advanced Open File Option used: No.
The network connection failed during the snapshot. Check the network, and then run the job again.
V-79-57344-34110 - AOFO: Initialization failure on: "\\DC01\System?State". Advanced Open File Option used: No.
The network connection failed during the snapshot. Check the network, and then run the job again.

Event viewer:
Event Type:      Error
Event Source:      Backup Exec
Event Category:      None
Event ID:      34113
Date:            12/05/2009
Time:            9:59:06 AM
User:            N/A
Computer:      DATA01
Description:
Backup Exec Alert: Job Failed
(Server: "DATA01") (Job: "Prudent Full Backup") Prudent Full Backup -- The job failed with the following error: A failure occurred accessing the SnapShot handle.

Event Type:      Warning
Event Source:      Backup Exec
Event Category:      Devices
Event ID:      33152
Date:            12/05/2009
Time:            9:57:31 AM
User:            N/A
Computer:      DATA01
Description:
Adamm Mover Error: Unload Status Retry!
Error = ERROR_NOT_READY
Drive = "IBM 1"
    {E2E4260B-3FD7-4112-A656-474797F2CF95}
Media = ""
    {00000000-0000-0000-0000-000000000000}
Read Mode: SingleBlock(0), ScsiPass(0)
Write Mode: SingleBlock(1), ScsiPass(1)

Event Type:      Error
Event Source:      Backup Exec
Event Category:      Devices
Event ID:      33152
Date:            12/05/2009
Time:            9:59:06 AM
User:            N/A
Computer:      DATA01
Description:
Adamm Mover Error: Unload Status Failure!
Error = ERROR_NOT_READY
Drive = "IBM 1"
    {E2E4260B-3FD7-4112-A656-474797F2CF95}
Media = ""
    {00000000-0000-0000-0000-000000000000}
Read Mode: SingleBlock(0), ScsiPass(0)
Write Mode: SingleBlock(1), ScsiPass(1)

Thank you for your help,
Simon