Thanks taca San,  the patch fixes the problem and it's
OK up to  'make package'.

Are all NetBSD versions OK with this patch ?
---
Makoto Fujiwara, 
Chiba, Japan, Narita Airport and Disneyland prefecture.

Index: distinfo
===================================================================
RCS file: /e/cvsync/cvsync/pkgsrc/lang/mono/distinfo,v
retrieving revision 1.28
diff -u -a -r1.28 distinfo
--- distinfo	4 Jan 2007 02:38:14 -0000	1.28
+++ distinfo	3 Aug 2007 14:52:31 -0000
@@ -22,3 +22,4 @@
 SHA1 (patch-ba) = 1aee2cf3dce0d2d378941b6cbff5600640c4d564
 SHA1 (patch-bc) = bbf1a903cf7fee1dbd3a070b0ef0d5aecbdf67e2
 SHA1 (patch-bd) = a52007ae22f8b23d20abf4a56e5b9d57ccd1fbbe
+SHA1 (patch-be) = d7a6232690ecd15c32ed44dcc498e596c248f332
Index: patches/patch-be
===================================================================
RCS file: patches/patch-be
diff -N patches/patch-be
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ patches/patch-be	3 Aug 2007 14:52:00 -0000
@@ -0,0 +1,18 @@
+$NetBSD$
+
+--- mono-1.1.13.8.1/support/sys-mman.corig	2006-04-11 07:21:37.000000000 +0900
++++ support/sys-mman.c	2007-08-03 22:04:18.000000000 +0900
+@@ -96,8 +96,13 @@
+ 	if (Mono_Posix_FromMremapFlags (flags, &_flags) == -1)
+ 		return MAP_FAILED;
+ 
++#if defined(__NetBSD__)
++	return mremap (old_address, (size_t) old_size, old_address, (size_t) new_size,
++			(unsigned long) _flags);
++#else
+ 	return mremap (old_address, (size_t) old_size, (size_t) new_size,
+ 			(unsigned long) _flags);
++#endif
+ }
+ #endif /* def HAVE_MREMAP */
+