Problems installing kubuntu on USB drive

[Rick Bowers]

I have a Dell Latitude D610 that I'm trying to install ubuntu on. It 
has a 100GB internal drive and I also have a 250GB external drive 
connected on the USB port.

When I run through the install "wizard", I get to step 5 asking me to 
select the installation disk.

It shows:
Select disk to install on
O /dev/sda (SCSI1) and
O /dev/sdb (SCSI3)

I select the second, /dev/sdb (SCSI3)

The next screen shows:
O Erase entire disk
O Manually edit the partition table

I select the 2nd option, then see the messages "Getting information 
about /dev/sda2

Eventually I see the partition list for /dev/sda, with what appears 
to be a drop-down to select /dev/sda or /dev/sdb.

At this point, the process is frozen. I cannot select <<Back, I 
cannot open the drop-down, nothing.

There is a "progress bar" above the partition list that shows in 
yellow, and slowly scrolls right, the resets to the left and scrolls 
right again, ad nauseum.

So, why does it show /dev/sda when I've selected /dev/sdb? Why can't 
I do anything from this screen (but kill the process)?

Any thoughts???

~Rick