SBS2008 & RDX320 blue screen

I have a brand-new ML350G6 installed with SBS2008. It's a clean install with only Sophos SBE and Acronis Backup & Restore installed. AD nor Exchange have yet been configured.

Today I added a HP StorageWorks RDX320 internal USB backupsystem.

I have connected the device to the internal USB port. On the first boot I get a BSOD, stop error

0x0000000A irql_not_less_or_equal

The system will not boot, even in safe mode. When I disconnect the RDX-device Windows will boot fine.

I tried connecting the device to a different USB port and even an External USB port.

I installed the latest firmware (3040) but to no avail.

I connected the RDX320 device to my Windows Vista x32 system and installed/used the device without any problems.

I tried plugging in the RDX320 on the ML350 after SBS2008 had already booted, got the message "installing driver" and after that blue screen, same error.

I also installed the latest RDX utility.

Nothing will work!

Any suggestions how to solve this problem?