Cut/Past in WDSc

Maybe I'm going about this all wrong, but I have two source members in 
different files.  Both are the same program, one has vendor updates in it. 
 I open them both up in WDSc using RSE (I think) and do a compare just to 
see what changed.  Then I want to copy the new one (vendors copy) over my 
old one (actual a copy checkout into Development under Aldon CMS).  I can 
delete all the lines in the old source member, by doing a select all and 
Cut.  But when I do a Select all and do a copy (of the new one) and try an 
past into the old one I get Nada!  Zip, Zero.  If I open up Word or some 
text editor it won't past either (mater of fact word will show me the 
clipboard and it is empty).

I know I could go do a "CPYF" and copy the new member to the old and 
replace it, but that leaves me room for errors, (ie: get wrong 
file/libr/mbr) where after I've just compared them I should stand a better 
chance of not messing it up.  In SEU I'd just split screen and do D99999 
to delete and C99999 to copy everything from the second one to the first 
and be done.  Can't seem to do that  in WDSc.  Am I using the wrong 
editor?  Wrong approach?  Not holding my mouth right?

This should be this hard, so I know I'm just doing something the way it's 
intended  And I need to get this figured out as my next vendor update is 
for one I can't do in SEU ( Yep, one of those unspeakable programs that is 
46,000 lines long!)  Better for them to maintain it than me.

Thanks for any suggestions and/or help.

-- Jim Lowary