diff -r f33b4770a078 Lib/idlelib/IOBinding.py
--- a/Lib/idlelib/IOBinding.py	Sun Oct 12 01:11:05 2014 -0400
+++ b/Lib/idlelib/IOBinding.py	Sun Oct 12 03:56:36 2014 -0400
@@ -500,15 +500,19 @@
 
     def defaultfilename(self, mode="open"):
         if self.filename:
-            return os.path.split(self.filename)
+            dirname, base = os.path.split(self.filename)
+            if base.startswith('~') and sys.platform[:3] == 'win':
+                # Fix Tcl/Tk Tilde Substitution problem on Windows
+                base = './' + base  # Escape the tilde
+            return dirname, base
         elif self.dirname:
             return self.dirname, ""
         else:
             try:
-                pwd = os.getcwd()
+                dirname = os.getcwd()
             except OSError:
-                pwd = ""
-            return pwd, ""
+                dirname = ""
+            return dirname, ""
 
     def asksavefile(self):
         dir, base = self.defaultfilename("save")