Rexx/Tk

I am trying to use combobox and get the following :

1. when using fvwm2/twm/cde window manager on aix the popup list always pops under the parent window

2. when using kde wm (rh linux) the list pops ok (displayed above the parrent window)

Parts of the popup list are visible only if the parent window isn't big enough to cover the list.

I tried to display from linux on window managers on aix and from aix on linux display - the aix window namagers always hide the popup window.
It happens with the demo that comes with rexxtk.
Rexxtk is 1.2, tcl/tk are 8.3 on linux and 8.4.9 on aix.

BTW(little bit ot): I had to expose unsupported command in rexxtkbase.c to make combobox work with tcl/tk 8.4.9:
"tk::unsupported::ExposePrivateCommand *\n"

TIA,
Jack