Highpoint SATA 1542 - Dell Server problem

Hello group,

I have a serious problem with a Dell Power Edge 2500 an a HighPoint
RocketRAID 1542 SATA controller card with two external RocketMate 1100
drives. The controller is recognized by the system and detected the
drives, the controller's BIOS is accessible, the server booted. After
installing the driver for the card the system hangs up when starting
the OS (Win NT4, SP6). I used the driver coming with the card and a
new downloaded version (jan, 19th).
The server is equipped with:
Power Edge Expandable RAID Controller 3/Di with a RAID 5 set
Adaptec AIC 7892 with a Sony TLS1100 tape library
The IRQ-config is:
Embedded serverworks IRQ 10
SLOT 7 / NIC IRQ 11
Embedded RAID Controller IRQ 7
Embedded RAID Controller IRQ 7
Embedded Adaptec SCSI IRQ 7
Embedded Adaptec SCSI IRQ 5
Anybody an idea?