fdisk freezing on USB flash under 6.3

I have a compact flash card plugged into a USB2 7-in-1 reader. The reader works fine in windows, and I can even mount the drive under QNX 6.3 and see the files on it.
However when I try to run fdisk, it freezes…
The CF shows up on /dev/hd2 (and /dev/hd2t77).
I do
fdisk /dev/hd2
fdisk /dev/hd2 info

and it simply freezes. (For a long time… hours… I’ve not seen it unfreeze).
It doesn’t respond to CTRL-C, although the OS is fine ; I can get another virtual terminal.

In 6.1 without USB support, we used to plug the CF cards into an IDE adapter, and then we could fdisk them no probs.
I was hoping to avoid using that special purpose build rig and just use a USB adapter on our normal QNX server;
is there anything special that I should do to partition a CF card hanging off a USB adapter?

I’ve tried this on a Dell Precision 340 and also on a much older USB1 machine ; same symptoms in both cases.
Michael Tomlinson
Invetech, Australia