If you set the following in your .screenrc the numpad keys will work
termcapinfo xterm ks@:ke@
I don't know if this will change any other important settings you might be using, however, so it would be worth giving things a test.
It might be that there is a better setting string, but so far I haven't been able to find one.
I've been searching around looking through termcap, terminfo, terminfo/termcap and screen manuals, but it looks like no-one is having much luck with getting both the number pad and the arrow keys in ncurses apps to work at the same time (they still seem to work in non-ncurses apps).
The closest I've seen is from these threads. Someone spoke to one of the program maintainers regarding an almost identical problem, however as of the 10th of March the problem wasn't resolved.