freebsd stable - Sep 2006 - Problem with aac0 on FreeBSD 6.1R/amd64

hi,

I have Dawning A950(4 CPUs) with raid card " Adaptec SCSI RAID
2230SLP".
when install FreeBSD 6.1R/amd64, everying is fine except probing aac:

aac0: COMMAND 0xffffffffxxxxxxxx TIMEOUT AFTER XXX SECONDS
kernel trap 12 with interrupts disabled.

This machine can install TurboLinux.

Thankfull for any advice

--hwh