diff --git a/src/libs/qtcreatorcdbext/extensioncontext.h b/src/libs/qtcreatorcdbext/extensioncontext.h
index 27a3f76b22e..5c7baad4362 100644
--- a/src/libs/qtcreatorcdbext/extensioncontext.h
+++ b/src/libs/qtcreatorcdbext/extensioncontext.h
@@ -90,6 +90,7 @@ public:
     // Return symbol group for frame (cached as long as frame/thread do not change).
     LocalsSymbolGroup *symbolGroup(CIDebugSymbols *symbols, ULONG threadId, int frame, std::string *errorMessage);
     int symbolGroupFrame() const;
+    void discardSymbolGroup();
 
     WatchesSymbolGroup *watchesSymbolGroup(CIDebugSymbols *symbols, std::string *errorMessage);
     WatchesSymbolGroup *watchesSymbolGroup() const; // Do not create.
@@ -105,7 +106,6 @@ public:
 
 private:
     bool isInitialized() const;
-    void discardSymbolGroup();
 
     IInterfacePointer<CIDebugControl> m_control;
     std::auto_ptr<LocalsSymbolGroup> m_symbolGroup;
diff --git a/src/libs/qtcreatorcdbext/qtcreatorcdbextension.cpp b/src/libs/qtcreatorcdbext/qtcreatorcdbextension.cpp
index ef3fd00ec0a..785efdcc8eb 100644
--- a/src/libs/qtcreatorcdbext/qtcreatorcdbextension.cpp
+++ b/src/libs/qtcreatorcdbext/qtcreatorcdbextension.cpp
@@ -125,6 +125,7 @@ static const CommandDescription commandDescriptions[] = {
  "-u uninitialized-list Comma-separated list of uninitialized inames\n"
  "-I formatmap          map of 'hex-encoded-iname=typecode'\n"
  "-T formatmap          map of 'hex-encoded-type-name=typecode'\n"
+ "-D                    Discard existing symbol group\n"
  "-W                    Synchronize watch items (-w)\n"
  "-w iname expression   Watch item"},
 {"watches",
@@ -403,6 +404,7 @@ static std::string commmandLocals(ExtensionCommandContext &commandExtCtx,PCSTR a
     StringVector uninitializedInames;
     InameExpressionMap watcherInameExpressionMap;
     bool watchSynchronization = false;
+    bool discardSymbolGroup = false;
     // Parse away options
     for (bool optionLeft = true;  optionLeft && !tokens.empty(); ) {
         switch (parameters.parseOption(&tokens)) {
@@ -446,6 +448,9 @@ static std::string commmandLocals(ExtensionCommandContext &commandExtCtx,PCSTR a
             case 'W':
                 watchSynchronization = true;
                 break;
+            case 'D':
+                discardSymbolGroup = true;
+                break;
             } // case option
         }
         break;
@@ -466,6 +471,8 @@ static std::string commmandLocals(ExtensionCommandContext &commandExtCtx,PCSTR a
         iname = tokens.front();
 
     const SymbolGroupValueContext dumpContext(commandExtCtx.dataSpaces(), commandExtCtx.symbols());
+    if (discardSymbolGroup)
+        extCtx.discardSymbolGroup();
     SymbolGroup * const symGroup = extCtx.symbolGroup(commandExtCtx.symbols(), commandExtCtx.threadId(), frame, errorMessage);
     if (!symGroup)
         return std::string();
diff --git a/src/plugins/debugger/cdb/cdbengine.cpp b/src/plugins/debugger/cdb/cdbengine.cpp
index d6d8440035b..8ad1c17f48a 100644
--- a/src/plugins/debugger/cdb/cdbengine.cpp
+++ b/src/plugins/debugger/cdb/cdbengine.cpp
@@ -1111,9 +1111,13 @@ void CdbEngine::updateLocals()
         watchHandler()->endCycle();
         return;
     }
-    // Watchers: Initial expand, get uninitialized and query
+    /* Watchers: Forcibly discard old symbol group as switching from
+     * thread 0/frame 0 -> thread 1/assembly -> thread 0/frame 0 will otherwise re-use it
+     * and cause errors as it seems to go 'stale' when switching threads.
+     * Initial expand, get uninitialized and query */
     QByteArray arguments;
     ByteArrayInputStream str(arguments);
+    str << "-D";
     // Pre-expand
     const QSet<QByteArray> expanded = watchHandler()->expandedINames();
     if (!expanded.isEmpty()) {
@@ -1428,7 +1432,9 @@ enum StopActionFlags
     StopShowExceptionMessageBox = 0x4,
     // Notify stop or just continue
     StopNotifyStop = 0x8,
-    StopIgnoreContinue = 0x10
+    StopIgnoreContinue = 0x10,
+    // Hit on break in artificial stop thread (created by DebugBreak()).
+    StopInArtificialThread = 0x20
 };
 
 unsigned CdbEngine::examineStopReason(const QByteArray &messageIn,
@@ -1483,8 +1489,12 @@ unsigned CdbEngine::examineStopReason(const QByteArray &messageIn,
             }
         }
         if (isDebuggerWinException(exception.exceptionCode)) {
+            unsigned rc = StopReportStatusMessage|StopNotifyStop;
+            // Detect interruption by DebugBreak() and force a switch to thread 0.
+            if (exception.function == "ntdll!DbgBreakPoint")
+                rc |= StopInArtificialThread;
             *message = msgInterrupted();
-            return StopReportStatusMessage|StopNotifyStop;
+            return rc;
         }
 #endif
         *exceptionBoxMessage = msgStoppedByException(description, QString::number(threadId));
@@ -1561,6 +1571,10 @@ void CdbEngine::handleSessionIdle(const QByteArray &messageBA)
             notifyInferiorSpontaneousStop();
         }
         // Start sequence to get all relevant data.
+        if (stopFlags & StopInArtificialThread) {
+            showMessage(tr("Switching to main thread..."), LogMisc);
+            postCommand("~0 s", 0);
+        }
         unsigned sequence = CommandListStack|CommandListThreads;
         if (debuggerCore()->isDockVisible(QLatin1String(Constants::DOCKWIDGET_REGISTER)))
             sequence |= CommandListRegisters;