A. First, determine which PCI slot the NetRAID-1Si is sitting in. Because of bus-mastering requirements, HP recommends that you place this 32-bit card in one of the LC 2000's 64-bit PCI slots (i.e., P5 or P6). HP also recommends that you place the Adaptec SCSI Card 29160 in one of the two PCI slots closest to P5 or P6 (i.e., P3 or P4).
Another possibility is that you have a loose or bad cable. Open the machine, and check the cable connections between the NetRAID-1Si and the LC 2000's SCSI backplane.
Finally, check the termination on any external devices that plug into the NetRAID-1Si. Better yet, for simplicity and performance reasons, plug any external devices into the LC 2000's integrated Adaptec SCSI or your Adaptec SCSI Card 29160 instead.
If none of these steps corrects the trouble, the fault might lie in the backplane itself. I've seen such problems occur on the LC 2000 as well as on HP's discontinued HP Netserver LH3 and HP Netserver LH4. In these situations, you might see drives go offline, SCSI timeouts—which could be the problem you're experiencing—and other erroneous behavior. Contact HP and ask them to replace the backplane.