The problem has been solved... I noticed that after the drive was plugged in the umass-enum died.  I could manually 
start it, plug in the device and it would die again.  So I took the drive out of the case, removed the jumper (no docs) 
and plugged back in. There was alot more led activity indicating a change.
I then did the mkdosfs, fdisk and a chkdosfs and all had positive results.  I could see /dev/hd10, /dev/hd10t12 and the 
chkdosfs came back fine. I still had no entry in the /fs so I tried 
mount -t dos /dev/hd10t12 /fs/hd10-dos-1
this resulted in a corrupted file system message.  As a test I deleted and redefined the partition as type 11 and the 
results were the same.

During this time I could plug and unplug the device from the usb incurring no problems with umass-enum.  So I decided to
 take the usb drive back to a windows box and format as fat32.  When I plugged the device back into the booted qnx box 
it came up as /dev/hd10, partition /dev/hd10t12 and /fs/hd10-dos-1.  If the drive is plugged in on boot this also works 
just fine.

So it looks like all this could have been avoided by removing the jumper and formating disk as dos on the windows 
machine at the start.  I still dont understand why the I could not mount the device after formatting on the qnx box.  ??
?

Thanks for your help,
Ann