diff -ur samba-3.0.5/source/lib/charcnv.c samba-3.0.5-fixed/source/lib/charcnv.c
--- samba-3.0.5/source/lib/charcnv.c	2004-04-04 13:37:36.000000000 +0600
+++ samba-3.0.5-fixed/source/lib/charcnv.c	2004-08-06 10:02:59.154773720 +0600
@@ -259,11 +259,11 @@
 			return destlen - o_len;
 
 		if (from == CH_UCS2 && to != CH_UCS2) {
-			/* Can't convert from ucs2 to multibyte. Just truncate this char to ascii. */
+			/* Can't convert from ucs2 to multibyte. Substitute with the default character. */
 			if (i_len < 2)
 				return destlen - o_len;
 			if (i_len >= 2) {
-				*outbuf = inbuf[0];
+				*outbuf = lp_default_char();
 
 				outbuf++;
 				o_len--;
@@ -279,11 +279,11 @@
 			goto again;
 
 		} else if (from != CH_UCS2 && to == CH_UCS2) {
-			/* Can't convert to ucs2 - just widen by adding zero. */
+			/* Can't convert to ucs2 - substitute with the default character. */
 			if (o_len < 2)
 				return destlen - o_len;
 
-			outbuf[0] = inbuf[0];
+			outbuf[0] = lp_default_char();
 			outbuf[1] = '\0';
 
 			inbuf++;
@@ -299,9 +299,9 @@
 			goto again;
 
 		} else if (from != CH_UCS2 && to != CH_UCS2) {
-			/* Failed multibyte to multibyte. Just copy 1 char and
+			/* Failed multibyte to multibyte. Just add default character and
 				try again. */
-			outbuf[0] = inbuf[0];
+			outbuf[0] = lp_default_char();
 
 			inbuf++;
 			i_len--;
@@ -581,12 +581,12 @@
 			goto out;
 
 		if (from == CH_UCS2 && to != CH_UCS2) {
-			/* Can't convert from ucs2 to multibyte. Just truncate this char to ascii. */
+			/* Can't convert from ucs2 to multibyte. Substitute with the default character. */
 			if (i_len < 2)
 				goto out;
 
 			if (i_len >= 2) {
-				*outbuf = inbuf[0];
+				*outbuf = lp_default_char();
 
 				outbuf++;
 				o_len--;
@@ -602,11 +602,11 @@
 			goto again;
 
 		} else if (from != CH_UCS2 && to == CH_UCS2) {
-			/* Can't convert to ucs2 - just widen by adding zero. */
+			/* Can't convert to ucs2 - substitute with the default character. */
 			if (o_len < 2)
 				goto out;
 
-			outbuf[0] = inbuf[0];
+			outbuf[0] = lp_default_char();
 			outbuf[1] = '\0';
 
 			inbuf++;
@@ -622,9 +622,9 @@
 			goto again;
 
 		} else if (from != CH_UCS2 && to != CH_UCS2) {
-			/* Failed multibyte to multibyte. Just copy 1 char and
+			/* Failed multibyte to multibyte. Just add default character and
 				try again. */
-			outbuf[0] = inbuf[0];
+			outbuf[0] = lp_default_char();
 
 			inbuf++;
 			i_len--;
diff -ur samba-3.0.5/source/param/loadparm.c samba-3.0.5-fixed/source/param/loadparm.c
--- samba-3.0.5/source/param/loadparm.c	2004-04-21 02:42:54.000000000 +0600
+++ samba-3.0.5-fixed/source/param/loadparm.c	2004-08-06 09:35:18.658207568 +0600
@@ -99,6 +99,7 @@
 	char *dos_charset;
 	char *unix_charset;
 	char *display_charset;
+	char default_char;
 	char *szPrintcapname;
 	char *szEnumPortsCommand;
 	char *szAddPrinterCommand;
@@ -763,6 +764,7 @@
 	{"dos charset", P_STRING, P_GLOBAL, &Globals.dos_charset, handle_charset, NULL, FLAG_ADVANCED}, 
 	{"unix charset", P_STRING, P_GLOBAL, &Globals.unix_charset, handle_charset, NULL, FLAG_ADVANCED}, 
 	{"display charset", P_STRING, P_GLOBAL, &Globals.display_charset, handle_charset, NULL, FLAG_ADVANCED}, 
+	{"default char", P_CHAR, P_GLOBAL, &Globals.default_char, NULL, NULL, FLAG_ADVANCED}, 
 	{"comment", P_STRING, P_LOCAL, &sDefault.comment, NULL, NULL, FLAG_BASIC | FLAG_ADVANCED | FLAG_SHARE | FLAG_PRINT}, 
 	{"path", P_STRING, P_LOCAL, &sDefault.szPath, NULL, NULL, FLAG_BASIC | FLAG_ADVANCED | FLAG_SHARE | FLAG_PRINT}, 
 	{"directory", P_STRING, P_LOCAL, &sDefault.szPath, NULL, NULL, FLAG_HIDE}, 
@@ -1329,6 +1331,9 @@
 	/* Use codepage 850 as a default for the dos character set */
 	string_set(&Globals.dos_charset, DEFAULT_DOS_CHARSET);
 
+	/* Use underscore by default instead of characters we can't convert */
+	Globals.default_char = '_';
+	
 	/*
 	 * Allow the default PASSWD_CHAT to be overridden in local.h.
 	 */
@@ -1611,6 +1616,7 @@
 FN_GLOBAL_STRING(lp_dos_charset, &Globals.dos_charset)
 FN_GLOBAL_STRING(lp_unix_charset, &Globals.unix_charset)
 FN_GLOBAL_STRING(lp_display_charset, &Globals.display_charset)
+FN_GLOBAL_CHAR(lp_default_char, &Globals.default_char)
 FN_GLOBAL_STRING(lp_logfile, &Globals.szLogFile)
 FN_GLOBAL_STRING(lp_configfile, &Globals.szConfigFile)
 FN_GLOBAL_STRING(lp_smb_passwd_file, &Globals.szSMBPasswdFile)
diff -ur samba-3.0.5/source/script/mkproto.awk samba-3.0.5-fixed/source/script/mkproto.awk
--- samba-3.0.5/source/script/mkproto.awk	2004-04-04 13:37:42.000000000 +0600
+++ samba-3.0.5-fixed/source/script/mkproto.awk	2004-08-06 09:49:48.346994776 +0600
@@ -98,6 +98,11 @@
   printf "int %s(void);\n", a[2]
 }
 
+/^FN_GLOBAL_CHAR/ {
+  split($0,a,"[,()]")
+  printf "char %s(void);\n", a[2]
+}
+
 /^static|^extern/ || !/^[a-zA-Z]/ || /[;]/ {
   next;
 }