Unable to boot squeeze on sw raid array when external USB drive connected

[Peter Tenenbaum <peter.g.tenenbaum@gmail.com>]

Hi there -- 

I am running squeeze with a non-RAID boot partition and a RAID-1 main partition.  I use GRUB2 as my bootloader.  My problem is the following:

When I have my Seagate FreeAgent USB hard drive connected to the computer, it's unable to boot, instead it hangs with the "Welcome to GRUB!" message on the screen.  Through copious use of echo statements, I've traced the problem down to the following code block near the top of grub.cfg:

insmod raid
insmod mdraid
insmod part_msdos
insmod part_msdos
insmod ext2

The first statement executes correctly; it hangs while trying to execute the second statement, insmod mdraid.

Any idea what the problem might be, and how to cure it?

Thanks in advance,
-PT