External usb HDD disconnects, system gets messed up

[Nezmer]

Hi,

FreeBSD 8.1-STABLE r215402M GENERIC  amd64

I'm having a weird issue. I have a 300GB external usb HDD with one ext2
partition. I use ZFS for my internal HDD.

Almost daily, The usb HDD disconnects(according to dmesg) and the system
gets messed up. Running processes keep responding but they would not
exit. And no new processes would start running. I eventually would have
to hard reset and run fsck.ext2 on the next run.

Any idea what's going on?
Do you need any specific information?