backspace issue

[caddy man]

when i type:

promt> bummer

and then i hit the backspace key i get:

promt> bummeRRRr

and the cursor refuses to go any further left

this makes me sad because i love screen, in fact i'm almost at the point 
to where i NEED screen.  any leads on how to solve this problem would be 
 greatly appreciated.  some info:

uname -a
Linux goth 2.6.8-gentoo-r1 #4 Fri Aug 20 08:52:31 MST 2004 i686 Intel(R) 
Pentium(R) 4 CPU 2.80GHz GenuineIntel GNU/Linux

screen -version
Screen version 4.00.02 (FAU) 5-Dec-03

aterm --version
0.4.2

it was working earlier, the only relevent thing that i changed since 
then (i think) was the .Xdefaults file

thx in advance,
Mike