The following patch speeds loading and closing a workspace to about half (at least on my system).
FindTargetsDebugger() is rebuilding the debugger menu system for every activation of a project. It does not need to do this during opening and closing of a workspace since after the workspace is loaded, CB will activated the correct project anyway.
It does not need to do it at all during closing of a workspace. With the patch, closing the CB workspace changed from 7 to less than 1 second.
Index: src/sdk/debuggermanager.cpp
===================================================================
--- src/sdk/debuggermanager.cpp	(revision 7937)
+++ src/sdk/debuggermanager.cpp	(working copy)
@@ -1146,7 +1146,10 @@
 }
 void DebuggerManager::FindTargetsDebugger()
-{
+{
+    if (Manager::Get()->GetProjectManager()->IsLoadingOrClosing())
+        return;
+
     m_activeDebugger = nullptr;
     m_menuHandler->SetActiveDebugger(nullptr);
svn build  rev 7937 (2012-04-23 04:29:22)   gcc 4.6.1 Windows/unicode - 32 bit