Problem booting via grub2 in software RAID system

[Peter Tenenbaum]

Hello there -- 

I have a Debian squeeze workstation which uses grub2 as its bootloader.  The system has 2 hard drives:  the root partition is a software RAID-1 array configured with mdadm; the boot partition is non-RAID (ext3).  It also has a DVD drive.  The underlying architecture is AMD64, the CPU and mobo are Intel.

Ordinarily, booting via grub2 with the configuration above works fine.  However, when I connect an external hard drive via a back-panel USB port, I can't boot -- the boot hangs or freezes or something.

Through use of echo statements, I determined that the problem occurs in the following stanza near the top of my grub.cfg file:

insmod raid
insmod mdraid
insmod part_msdos
insmod part_msdos
insmod ext2

The first statement executes correctly, but the second (insmod mdraid) is the one which hangs.

Any suggestions for what might be wrong and/or how to correct it?

Thanks in advance for any help you can provide,
-PT