Index: /trunk/src/VBox/Main/src-server/MediumImpl.cpp
===================================================================
--- /trunk/src/VBox/Main/src-server/MediumImpl.cpp	(revision 71096)
+++ /trunk/src/VBox/Main/src-server/MediumImpl.cpp	(revision 71097)
@@ -3042,4 +3042,13 @@
                 suffix.toLower();
                 destPath.stripSuffix().append('.').append(suffix);
+            }
+
+            /* Simple check for existence */
+            if (RTFileExists(destPath.c_str()))
+            {
+                rc = setError(VBOX_E_FILE_ERROR,
+                              tr("The given path '%s' is an existing file. Delete or rename this file."),
+                              destPath.c_str());
+                throw rc;
             }