grub2 hangs / freezes when external USB hard drive is connected

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

Hi everyone -- 

My squeeze home machine cannot boot when an external hard drive is connected via USB.  When the drive is disconnected, booting occurs normally; but when it is connected, I get a "Welcome to Grub!" message and then nothing further happens.

I've tried going into the boot menu in BIOS and setting the boot order so that the external hard drive is used last, but I still have this problem.  It seems like it must be at least partially successful in booting off the internal hard drives, since they have grub2 installed but the external hard drive does not.

Any suggestions for how I can configure the system so that it does not get into trouble when the external hard drive is connected?

Thanks in advance,
-PT