@npanag

had similar problems, ie my u1 did not find the harddrive in os4.1. replaced the backup battery and the problem disappeared.

@MamePPCA1

did you try the highest udma settings ? I do not know if udma5 is the highest on your machine. if udma6 is the highest for example, give it a try as well..

@MamePPCA1

open the prefs drawer and doubleklick on the UBoot icon.
in the IDE ports tab, select UDMA5 transfer mode for your harddrive and then click save. reboot.

but, this tip is for the micro, I mixed up your configuration while reading the thread so it's possible that this solution doesn't apply to your problem...

@MamePPCA1

had similar problems just uptil now.. my micro started to freeze during network traffic, but when I changed to udma5 from udma4 everything works just fine.( so far though.). this change can be made in the UBoot preferences.