Haven't replaced /dev/hdb yet.
Is there some way of getting it ignored in the following scenario?

I started aptitude.
It told me it hadn't been cleanly shut down last time, and recommended 
I do
    dpkg --configure -a
before I do anything else.

I do that, and the system apparently does some cleanup, generating
initrd images, and then starts to update grub.

Update-grub stalls on block 51 of device /dev/hdb, trying to do
something with it over and over (as presented on the main system
console, which is *not* the one I'm trying to run aptitude on)

Now evidently /dev/hdb is not working and will need to be replaced.

But isn't there some way to tell grub to ignore /dev/hdb?
What is it that controls which drives grub tries to work with.
It must get this from somewhere. I did not specify or mention /dev/hdb
anywhere in my dpkg --configure -a. And there are several other drives
I could use to install grub and a boot record. I can even use the
grub-install command to do so. So why, oh why, does it pick on
/dev/sdb?

-- hendrik