Adamm Mover Error: Write Failure! during a backup process

I have two devices:
- HP  ML350 Server with a SCSI Adapter connected via PCI: LSI Adapter, Ultra320 SCSI 2000 Series.
- HP LTO Ultrium-3 drive with a 1x8 G2 autoloader (x86based) connected to the SCSI Adapter..

Windows 2003 R2 Server installed with the last drivers of the tape installed. It seems installed correctly due to the SCSI adapter, plus the tape drive and the medium changers are detected fine in the device manager. At least without errors.

Using the Backup Exec utility to do the backups write errors were detected. After that i could execute the HP StorageWorks Library and Tape Tools to check if the problem is in the device or in backup exec drivers. These tools detected the same error, which was written in the event viewer errors:
Event viewer Error 1:
Adamm Mover Error: Write Failure!
Error = ERROR_IO_DEVICE
Drive = "HP 1"
    {F4F2A1B4-8FF5-4C50-8842-D1F1FB6CE171}
Media = "LTO000003"
    {981AFCC9-046B-4B1F-82E3-8E00B2E07987}
Read Mode: SingleBlock(0), ScsiPass(0)
Write Mode: SingleBlock(1), ScsiPass(1)

Event Viewer Error 2:
An unknown error occurred on device "HP 1".

 For more information, click the following link:
http://eventlookup.veritas.com/eventlookup/EventLookup.jhtml

Event Viewer Error 3:
Backup Exec Alert: Job Failed
(Server: "ESMDPPFS001") (Job: "Test LTO3") Test LTO3 -- The job failed with the following error: A hardware error occurred.
 
 For more information, click the following link:
http://eventlookup.veritas.com/eventlookup/EventLookup.jhtml

The Autoloader has at the moment 7 Tapes for writting and another one for cleansing. All of them without write protection.

I could read that one of the possible reasons could be the SCSI connection.

Thanks for your support and your ideas to solve this problem,