Richard,
in both GRASS 4.2.1 source and binary packages new libcurses
are included:
../linux_libraries/elf_libcurses.tar.gz
If you _deinstall_ the old libcurses and install the
new ones afterwards, you problem will be solved (it
has also taken hours of my life once to get that idea).
Follow the instructions in that specific directory.
I hope this helps
Markus