Following patch should fix the problem.
Index: devel/ncurses/builtin.mk
===================================================================
RCS file: /cvsroot/pkgsrc/devel/ncurses/builtin.mk,v
retrieving revision 1.13
diff -u -r1.13 builtin.mk
--- devel/ncurses/builtin.mk 25 Feb 2008 04:19:34 -0000 1.13
+++ devel/ncurses/builtin.mk 26 Feb 2008 07:48:51 -0000
@@ -74,6 +74,7 @@
# XXX
. if ${OPSYS} == "NetBSD"
USE_BUILTIN.ncurses= yes
+H_NCURSES= /usr/include/curses.h
. endif
#
# Some platforms don't have a curses implementation that can replace