diff --git a/IPython/frontend/qt/console/console_widget.py b/IPython/frontend/qt/console/console_widget.py
index b45e971..915783d 100644
--- a/IPython/frontend/qt/console/console_widget.py
+++ b/IPython/frontend/qt/console/console_widget.py
@@ -192,7 +192,7 @@ class ConsoleWidget(Configurable, QtGui.QWidget):
         elif etype == QtCore.QEvent.MouseButtonRelease and \
                 event.button() == QtCore.Qt.MidButton and \
                 obj == self._control.viewport():
-            cursor = self._control.cursorForPosition(event.pos());
+            cursor = self._control.cursorForPosition(event.pos())
             self._control.setTextCursor(cursor)
             self.paste(QtGui.QClipboard.Selection)
             return True
@@ -578,31 +578,46 @@ class ConsoleWidget(Configurable, QtGui.QWidget):
         self._show_prompt()
         self.input_buffer = input_buffer
 
+    def _cancel_text_completion(self):
+        """ If text completion is progress, cancel it.
+        """
+        if self._text_completing_pos:
+            self._clear_temporary_buffer()
+            self._text_completing_pos = 0
+
     def _clear_temporary_buffer(self):
         """ Clears the "temporary text" buffer, i.e. all the text following
             the prompt region.
         """
+        # Select and remove all text below the input buffer.
         cursor = self._get_prompt_cursor()
-        if cursor.movePosition(QtGui.QTextCursor.NextBlock):
-            prompt = self._continuation_prompt.lstrip()
-            while True:
-                temp_cursor = QtGui.QTextCursor(cursor)
-                temp_cursor.select(QtGui.QTextCursor.BlockUnderCursor)
-                text = str(temp_cursor.selection().toPlainText()).lstrip()
-                if not text.startswith(prompt) or \
-                        not cursor.movePosition(QtGui.QTextCursor.NextBlock):
-                    break
-            cursor.movePosition(QtGui.QTextCursor.Left) # Grab the newline.
-            cursor.movePosition(QtGui.QTextCursor.End,
-                                QtGui.QTextCursor.KeepAnchor)
-            cursor.removeSelectedText()
+        prompt = self._continuation_prompt.lstrip()
+        while cursor.movePosition(QtGui.QTextCursor.NextBlock):
+            temp_cursor = QtGui.QTextCursor(cursor)
+            temp_cursor.select(QtGui.QTextCursor.BlockUnderCursor)
+            text = str(temp_cursor.selection().toPlainText()).lstrip()
+            if not text.startswith(prompt):
+                break
+        else:
+            # We've reached the end of the input buffer and no text follows.
+            return
+        cursor.movePosition(QtGui.QTextCursor.Left) # Grab the newline.
+        cursor.movePosition(QtGui.QTextCursor.End,
+                            QtGui.QTextCursor.KeepAnchor)
+        cursor.removeSelectedText()
+
+        # After doing this, we have no choice but to clear the undo/redo
+        # history. Otherwise, the text is not "temporary" at all, because it
+        # can be recalled with undo/redo. Unfortunately, Qt does not expose
+        # fine-grained control to the undo/redo system.
+        if self._control.isUndoRedoEnabled():
+            self._control.setUndoRedoEnabled(False)
+            self._control.setUndoRedoEnabled(True)
 
     def _complete_with_items(self, cursor, items):
         """ Performs completion with 'items' at the specified cursor location.
         """
-        if self._text_completing_pos:
-            self._clear_temporary_buffer()
-            self._text_completing_pos = 0
+        self._cancel_text_completion()
 
         if len(items) == 1:
             cursor.setPosition(self._control.textCursor().position(), 
@@ -785,9 +800,7 @@ class ConsoleWidget(Configurable, QtGui.QWidget):
                 intercepted = True
                 
                 # Special handling when tab completing in text mode.
-                if self._text_completing_pos:
-                    self._clear_temporary_buffer()
-                    self._text_completing_pos = 0
+                self._cancel_text_completion()
 
                 if self._in_buffer(position):
                     if self._reading:
@@ -1251,8 +1264,7 @@ class ConsoleWidget(Configurable, QtGui.QWidget):
         """ Cancels the current editing task ala Ctrl-G in Emacs.
         """
         if self._text_completing_pos:
-            self._clear_temporary_buffer()
-            self._text_completing_pos = 0
+            self._cancel_text_completion()
         else:
             self.input_buffer = ''
         
diff --git a/IPython/frontend/qt/console/ipython_widget.py b/IPython/frontend/qt/console/ipython_widget.py
index b889ae3..0667341 100644
--- a/IPython/frontend/qt/console/ipython_widget.py
+++ b/IPython/frontend/qt/console/ipython_widget.py
@@ -138,17 +138,22 @@ class IPythonWidget(FrontendWidget):
                 info.pos == cursor.position():
             matches = rep['content']['matches']
             text = rep['content']['matched_text']
-
-            # Clean up matches with '.'s and path separators.
-            parts = re.split(r'[./\\]', text) 
-            sep_count = len(parts) - 1
-            if sep_count:
-                chop_length = sum(map(len, parts[:sep_count])) + sep_count
-                matches = [ match[chop_length:] for match in matches ]
-                text = text[chop_length:]
+            offset = len(text)
+
+            # Clean up matches with period and path separators if the matched
+            # text has not been transformed. This is done by truncating all
+            # but the last component and then suitably decreasing the offset
+            # between the current cursor position and the start of completion.
+            if len(matches) > 1 and matches[0][:offset] == text:
+                parts = re.split(r'[./\\]', text) 
+                sep_count = len(parts) - 1
+                if sep_count:
+                    chop_length = sum(map(len, parts[:sep_count])) + sep_count
+                    matches = [ match[chop_length:] for match in matches ]
+                    offset -= chop_length
 
             # Move the cursor to the start of the match and complete.
-            cursor.movePosition(QtGui.QTextCursor.Left, n=len(text))
+            cursor.movePosition(QtGui.QTextCursor.Left, n=offset)
             self._complete_with_items(cursor, matches)
 
     def _handle_execute_reply(self, msg):