Keymapping woes

My setup:

xt5250 version 0.16.5
kubuntu 6.06

My problem:

My F24 key seems to be completely disabled when using xt5250.  This may
not be related to xt5250 but I'm hoping that someone can point me in the
right direction.  By disabled I mean that whenever I press Shift + F12
nothing happens.  I don't even get an error message when I press F24
when using AS/400 programs that don't have F24 defined.  That's why I
think it's never even making it to xt5250.

By default my XTerm file doesn't define F24 so I tried the following
definitions (one at a time):

Shift <Key>F12: string("\033+") \n\
Shift <Key>F12: string("\033[38") \n\

Neither of them worked.  I have confirmed that the first one (033+) is
the correct octal value by putting a definition for F23 in my XTerm file
using that code.  When I did that, pressing F23 behaved just like I'd
pressed F24.

I'm wondering if some other file somewhere is interfering with tn5250
sending the signal for the F24 key.  Anyone have any ideas as to what
might be causing me grief?

I have confirmed that KDE doesn't have the key bound to any special
function by going to System Settings -> Regional & Accessibility and
checking the Input Actions and Keyboard Shortcuts areas.

Thanks in advance for any help or pointers!
Benny