Index: /trunk/src/VBox/Main/src-client/GuestCtrlImpl.cpp
===================================================================
--- /trunk/src/VBox/Main/src-client/GuestCtrlImpl.cpp	(revision 35539)
+++ /trunk/src/VBox/Main/src-client/GuestCtrlImpl.cpp	(revision 35540)
@@ -2123,5 +2123,9 @@
                         }
                         else
-                            vrc = VERR_NO_DATA; /* This is not an error we want to report to COM. */
+                        {
+                            /* No data within specified timeout available. Use a special
+                             * error so that we can gently handle that case a bit below. */
+                            vrc = VERR_NO_DATA;
+                        }
                     }
                     else /* If callback not called within time ... well, that's a timeout! */
@@ -2137,5 +2141,6 @@
                     if (vrc == VERR_NO_DATA)
                     {
-                        /* This is not an error we want to report to COM. */
+                        /* If there was no output data then this is no error we want
+                         * to report to COM. The caller just gets back a size of 0 (zero). */
                         rc = S_OK;
                     }