* file.c (rb_file_s_dirname): UNC consists from "server" portion and
  "share" portion.  fixed: [ruby-core:05076]


Index: file.c
===================================================================
RCS file: /cvs/ruby/src/ruby/file.c,v
retrieving revision 1.199
diff -U2 -p -r1.199 file.c
--- file.c	18 Apr 2005 15:01:19 -0000	1.199
+++ file.c	24 May 2005 06:23:14 -0000
@@ -2720,6 +2720,6 @@ rb_file_s_dirname(klass, fname)
     root = skiproot(name);
 #ifdef DOSISH_UNC
-    if (root > name + 2 && isdirsep(*name))
-	name = root - 2;
+    if (root > name + 1 && isdirsep(*name))
+	root = skipprefix(name = root - 2);
 #else
     if (root > name + 1)