Index: /trunk/src/VBox/Main/src-server/BandwidthControlImpl.cpp
===================================================================
--- /trunk/src/VBox/Main/src-server/BandwidthControlImpl.cpp	(revision 41848)
+++ /trunk/src/VBox/Main/src-server/BandwidthControlImpl.cpp	(revision 41849)
@@ -412,4 +412,8 @@
 STDMETHODIMP BandwidthControl::CreateBandwidthGroup(IN_BSTR aName, BandwidthGroupType_T aType, LONG64 aMaxBytesPerSec)
 {
+    if (aMaxBytesPerSec <= 0)
+        return setError(E_INVALIDARG,
+                        tr("Bandwidth group limit must be positive"));
+
     AutoCaller autoCaller(this);
     if (FAILED(autoCaller.rc())) return autoCaller.rc();
Index: /trunk/src/VBox/Main/src-server/BandwidthGroupImpl.cpp
===================================================================
--- /trunk/src/VBox/Main/src-server/BandwidthGroupImpl.cpp	(revision 41848)
+++ /trunk/src/VBox/Main/src-server/BandwidthGroupImpl.cpp	(revision 41849)
@@ -284,4 +284,8 @@
 STDMETHODIMP BandwidthGroup::COMSETTER(MaxBytesPerSec)(LONG64 aMaxBytesPerSec)
 {
+    if (aMaxBytesPerSec <= 0)
+        return setError(E_INVALIDARG,
+                        tr("Bandwidth group limit must be positive"));
+
     AutoCaller autoCaller(this);
     if (FAILED(autoCaller.rc())) return autoCaller.rc();