Reboot hangs on xeon server

[Christopher McGee]

The server I have is using an Intel SE7501CW2 server board with 1 Xeon 
2.0Ghz processor.  It's got a Mylex AcceleRAID 170 card with 6 - 36GB 
scsi drives.  When I reboot the machine, via ctrl-alt-del, or typing 
reboot, it syncs disks, then gives the messages:

All buffers synced.
Uptime: ##m##s

At this point, it just hangs forever and has to be powercycled.  I've 
tried installing 4.11, 5.4 and 6.0 on this box.  The only version that 
works properly is 4.11, however, at this point I would prefer to not put 
another 4.x box in production.  I have tried booting in safe mode and 
rebooting and I get the same result.  I've tried disabling usb in the 
bios, in the kernel, and in both, and it still has the same results.

Any ideas what could fix this?

Chris