Index: /trunk/src/VBox/Main/HardDiskImpl.cpp
===================================================================
--- /trunk/src/VBox/Main/HardDiskImpl.cpp	(revision 360)
+++ /trunk/src/VBox/Main/HardDiskImpl.cpp	(revision 361)
@@ -2254,5 +2254,5 @@
                         "the hard disk image file '%s' doesn't match "
                         "UUID {%Vuuid} stored in the registry"),
-                    parentId.ptr(), mParent->toString().raw(),
+                    parentId.raw(), mParent->toString().raw(),
                     filePath.raw(), mParent->id().raw());
                 break;
@@ -2262,7 +2262,8 @@
         {
             errMsg = Utf8StrFmt (
-                tr ("Hard disk image '%s' is a differencing image and "
-                    "cannot be opened directly"),
-                filePath.raw());
+                tr ("Hard disk image '%s' is a differencing image that is linked "
+                    "to a hard disk with UUID {%Vuuid} and cannot be used "
+                    "directly as a base hard disk"),
+                filePath.raw(), parentId.raw());
             break;
         }