3ware 9500 problems

[bfranco at uolsinectis.com.ar]

Hi everyone in the list.

I'm having problems with a 3ware 9500s - 8 ports (with 4 x WDC WD1600JD-22HBB0 SATA 150 in RAID 5). 
Every 10 days or so my server shuts down uncleanly. It used to happen almost every day until I added hint.acpi.0.disabled="1" to my loader.conf.

Syslog reports:
...
Apr  8 12:06:42 titan kernel: twa0: ERROR: (0x04: 0x003a): Drive power on reset detected: port=3
Apr  8 12:06:42 titan kernel: twa0: ERROR: (0x04: 0x0025): Error flushing cached write data to disk: unit=0
Apr  8 12:06:42 titan kernel: twa0: ERROR: (0x04: 0x0002): Degraded unit detected: unit=0, port=3
Apr  8 12:08:04 titan kernel: twa0: INFO: (0x04: 0x000b): Rebuild started: unit=0
Apr  8 13:13:34 titan syslogd: kernel boot file is /boot/kernel/kernel
Apr  8 13:13:34 titan kernel: Copyright (c) 1992-2005 The FreeBSD Project.
Apr  8 13:13:34 titan kernel: Copyright (c) 1979, 1980, 1983, 1986, 1988, 1989, 1991, 1992, 1993, 1994
...

Does anyone have any clue about what's going on? I have another server, same configuration but with a 3ware 7500 - 4 ports (ATA) , and it works great.

Motherboard is Tyan S5120AGNF (tomcat i915g).
Processor is a PIV 530J 3Ghz (disabled ht from bios).
twa support is enabled in kernel (5.3-STABLE FreeBSD 5.3-STABLE #2).

Thanks in advance.