Ever since I got my pi almost a week ago I've been having issues with it locking up or freezing when accessing my external usb drives. This issue happens with both Debian Squeeze and Arch Linux.
Not sure what is causing it, so I will list what I'm using.
HTC micro usb adaptor rated 5v - 1A
Sandisk class 6 8gb SD card (have tried others also)
Two Western Digital 3.5" external USB 2 drives both are self powered.
Generic keyboard and mouse and also a hub.
The issue seems to happen with the hub, keyboard and mouse of the equation. Especially if I am copying files across the network to my samba share on one of the external drives. My Pi will just freeze up after awhile requiring a full reset. Seems to run fine when usb is not acessed.
I've also attached a screenshot of the latest crash from debian squeeze.