Index: /trunk/src/VBox/Main/src-server/MachineImpl.cpp
===================================================================
--- /trunk/src/VBox/Main/src-server/MachineImpl.cpp	(revision 35983)
+++ /trunk/src/VBox/Main/src-server/MachineImpl.cpp	(revision 35984)
@@ -938,4 +938,10 @@
     if (FAILED(autoCaller.rc())) return autoCaller.rc();
 
+    // prohibit setting a UUID only as the machine name, or else it can
+    // never be found by findMachine()
+    Guid test(aName);
+    if (test.isNotEmpty())
+        return setError(E_INVALIDARG,  tr("A machine cannot have a UUID as its name"));
+
     AutoWriteLock alock(this COMMA_LOCKVAL_SRC_POS);
 
Index: /trunk/src/VBox/Main/src-server/SnapshotImpl.cpp
===================================================================
--- /trunk/src/VBox/Main/src-server/SnapshotImpl.cpp	(revision 35983)
+++ /trunk/src/VBox/Main/src-server/SnapshotImpl.cpp	(revision 35984)
@@ -349,4 +349,10 @@
     HRESULT rc = S_OK;
     CheckComArgStrNotEmptyOrNull(aName);
+
+    // prohibit setting a UUID only as the machine name, or else it can
+    // never be found by findMachine()
+    Guid test(aName);
+    if (test.isNotEmpty())
+        return setError(E_INVALIDARG,  tr("A machine cannot have a UUID as its name"));
 
     AutoCaller autoCaller(this);