I have personally fought with this issue on two IBM servers. Both systems crashed while attempting to load Veritas BackupExec device drivers.

Microsoft knowledgebase article 821138 says:
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SYMPTOMS
A Windows Server 2003-based computer may stop responding, and you may receive a DRIVER_IRQL_NOT_LESS_OR_EQUAL (0xD1) Stop error. This may occur if your computer has a CD-ROM drive or tape device that is connected to a small computer system interface (SCSI) controller that uses the Storport.sys driver.

CAUSE
This problem occurs because the SCSI controller port driver (Storport.sys) contains a code defect. The Storport.sys driver incorrectly completes a request twice, and this causes the computer to stop responding.
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a HotFix is available to address this issue