delete does not work properly under X Window

[Jan Krupa <krupa@alpha.sggw.waw.pl>]

I debian2.0 on Pentium. 

The key delete works (under X Window) the same way as backspace does I
mean
both keys erase a letter on the left side of cursor.
The key delete works O.K. on the console
(it erases a letter on right side of cursor).

I have tried to put in .Xmodemap the following

keycode 22 = BackSpace
keycode 107 = Delete

or 

keycode 0x16 = BackSpace
keycode 0x6B = Delete

but it does not help, the keys work as before.

Could someone please suggest how can I achieve the
delete key work properly (I would like delete key
to erase a letter on right side of cursor).

Jan