Megaraid lockup on 2.6.[7-8]

This dump is from 2.6.7-rc3. I'm using the in-kernel megaraid driver on this Express 500.

0000:00:09.0 RAID bus controller: American Megatrends Inc. MegaRAID (rev 02)
Subsystem: American Megatrends Inc. MegaRAID 475 Express
500/500LC RAID Controller

At this point, I'm really unsure what's going on. It went from "working" to "not working"
overnight, after a 2 month uptime with no problem. Now it lasts between 5 minutes and 3 hours before it locks up. Somtimes the lockups are 'soft', in that all disk IO hangs in wait. Othertimes it's hard (kernel panic and reload)

Due to the sudden nature of the problem, I suspected hardware. Starting with the SCSI cable,
RAID card, RAM, PCI riser card, motherboard... it's all been replaced.
The megaraid itself
dosn't complain about problems accessing the drives (and the state is always Optimal on reboot, no media or "other" errors on any drive)

Software wise, I've tried from 2.6.7-rc3, 2.6.7, 2.6.8-rc2 and 2.6.8-rc3.

I tried the 2.20 series, but they don't appear to recognize older cards? Are they for
U320 only or did I do something wrong? (2.20 works fine on another box with a U320 controller)

I'm at a loss. I guess I could replace all the drives, being as that's the last thing left to try,
but A) it's a serious PITA and B) they "appear" fine, even when doing a full consistency check
via the Ctrl-M BIOS.

This is made even more fun due to the fact it's a LIVE server, or was, until two days ago. It's
also stored in a colo facility about an hour from my house. I'm
going to go back tomorrow
and try updating the firmware on the megaraid, but that's about the only thing I can think
left to try. Perhaps some PCI setting I should try?

Any help would be greatly appreciated!

(Different PCI Bus/Slot due to being in a different MB when I captured this backtrace)

megaraid: found 0x101e:0x1960:bus 1:slot 2:func 0 scsi0:Found MegaRAID controller at 0xf8846000, IRQ:27
megaraid: [C170:3.13] detected 1 logical drives.
megaraid: supports extended CDBs.
megaraid: channel[0] is raid.
scsi0 : LSI Logic MegaRAID C170 254 commands 16 targs 4 chans 7 luns
scsi0: scanning scsi channel 0 for logical drives.
Vendor: MegaRAID Model: LD 0 RAID5 210G Rev: C170
Type: Direct-Access ANSI SCSI revision: 02
SCSI device sda: 430116864 512-byte hdwr sectors (220220 MB)
sda: asking for cache data failed
sda: assuming drive cache: write through
/dev/scsi/host0/bus0/target0/lun0: p1
Attached scsi disk sda at scsi0, channel 0, id 0, lun 0 Attached scsi generic sg0 at scsi0, channel 0, id 0, lun 0, type 0
scsi0: scanning scsi channel 1 for logical drives.
scsi0: scanning scsi channel 2 for logical drives.
scsi0: scanning scsi channel 4 [P0] for physical devices.
...
megaraid: ABORTING-12793 cmd=2a <c=0 t=0 l=0>
megaraid: ABORTING-12796 cmd=2a <c=0 t=0 l=0>
megaraid: ABORTING-12797 cmd=2a <c=0 t=0 l=0>
megaraid: ABORTING-12798 cmd=2a <c=0 t=0 l=0>
megaraid: reservation reset failed.
megaraid: RESET-12793 cmd=2a <c=0 t=0 l=0>
megaraid: reservation reset failed.
megaraid: RESET-12793 cmd=2a <c=0 t=0 l=0>
megaraid: reservation reset failed.
megaraid: RESET-12793 cmd=2a <c=0 t=0 l=0>
scsi: Device offlined - not ready after error recovery: host 0 channel 0 id 0 lun 0
scsi: Device offlined - not ready after error recovery: host 0 channel 0 id 0 lun 0
scsi: Device offlined - not ready after error recovery: host 0 channel 0 id 0 lun 0
scsi: Device offlined - not ready after error recovery: host 0 channel 0 id 0 lun 0
SCSI error : <0 0 0 0> return code = 0x6000000
end_request: I/O error, dev sda, sector 197231
Buffer I/O error on device dm-64, logical block 24598
lost page write due to I/O error on dm-64
scsi0 (0:0): rejecting I/O to offline device

Given that it's kept in a 70 degree machine room, I don't think it's temperature related.

It's a 450 watt redundant powersupply. It's possible that it has failed, but unlikely. (both halves
are independant)

Wouldn't power supply/thermal problems manifest as random errors,
though? Memory generally
fails the same way if it's a specific address flaking out (and that address is in kernel space) but
I've already replaced it.

Also, I checked the archives and I'm not the only one that's getting this. Apparently it's a 2.6 specific problem, 2.4 did not have it.

What is the latest driver for a LSI Megaraid Express 500? As I said, 2.20 seems to be only for
the U320/SATA cards, or at least it dosn't detect mine.