Dual keyboards no longer work properly in latest X

[David Wake]

I have just reimaged my machine from SuSe 10.1 to Fedora 11.  My old
version of X (from SuSe) was probably 6.9.0. My new version of X (from
Fedora) is xorg-x11-server-Xorg-1.6.3-4.fc11.

I have two USB keyboards plugged into my machine. With my old
installation I used to be able to combine a modifier key from one
keyboard with a regular key from the other. For example I could press
shift on the left keyboard and ¨a¨ on the right keyboard, and the
result would be upper-case¨A¨ (exactly the same as if I pressed shift
and ¨a¨ both on the right keyboard).

After installing Fedora 11, this works properly in a text-only console
(e.g. after pressing Ctrl + Alt + F2), but it doesn´t work properly in
the GUI. What happens is that the first key stroke using a new
modifier lacks that modifier. Subsequent key strokes do include the
modifier. For example, if I hold down Shift and ¨a¨ repeatedly, I get
aAAAAAAAAA (so the first ¨a¨ is lower case).

Since this still works correctly in a text console, I've concluded
that the upgrade of X is the most likely explanation for this problem.
 I've tried multiple environments (KDE, GNOME) and the problem doesn't
go away,

This is driving me nuts because I am used to using two separate
keyboards, one for each hand. Does anyone have any ideas on how to
debug or fix this? Even a clue as to how to debug X's handling of
modifier keys would be very welcome!

Cheers

David