grub on usb pen drive stuck after stage 1

[john terragon]

Hi.

So I'm having this problem with grub (2) and a pen drive (and probably the bios 
of the laptop, because that seems to
be the source of the problem). I've a fully encrypted linux installation
and I use a usb pen drive to boot into it. The pen drive contains the usual 
stuff that goes in a /boot dir (kernel
image initrd the grub subdir etc). I installed grub on the pen drive with this 
command (from another linux installation)


grub-install --recheck --boot-directory=/mnt/sdb1/boot/ /dev/sdb

where /dev/sdb is the pern drive, /dev/sdb1 (mounted on /mnt/sdb1) is the first 
partition on the pen drive where the /boot dir is.
Installation ends without errors. But when I try to boot from the pen drive I 
get the first few words from grub and after the 

phrase "Welcome to GRUB!" I get a blinking cursor and the laptop is in hard 
lock (i.e. crtl-alt-canc doesn't work and I have to turn it off
and on again). Now the peculiar thing is that if I tried the pen drive on any 
other computer I could get my hands on and it works perfectly.
So the installation on the pen drive seems to have been done correctly but on 
that particular laptop grub hangs after stage 1. I don't 

know if the old terminology of grub 1 still applies to grub 2 but anyway grub  
seems to hang in a phase where it has to read part of
its code by accessing directly the pen drive (and not through a file system as 
in the later stage).
Some random notes on the system:

-I'm using debian unstable with grub 2.00
-no UEFI (well the bios is probably UEFI since it's InsydeH2O but the legacy 
interface is used) 

 or GPT partition
-as I wrote the installation of grub on that pen drive works perfectly on a 
many other computers, some with uefi some without.

Any ideas?

Thanks 

john