USB-problems on ML 115 G1

[Theo Richel]

I have two printers and an external harddisk (LaCie D2 Quadra) connected through USB. They are recognized as such when I plug them in but the software refuses to install for the printer and the external hd is not available.

Also when I connect this same external hd to an external Sata port I get a bsod which is supposed to be related to partmgr.sys. Updating that file has no effect though.

I was advised to test my memory, but the disks a created for this refuse to boot on my server (they do boot elsewhere).
I know it sounds strange but apart from this the system runs allright.
Suggestions to solve this would be very very welcome. Many thanks in advance.