I have just seen http://support.microsoft.com/default.aspx?...kb;EN-US;290780. I think it throws some light on why we have all found (in earlier threads) application_startup not firing dependably when we try to catch it from an OTM, but was dependable from a COM addin.

Basically the KBA says if you move a OTM to another user's computer "the Application_Startup event doesn't fire, or other macro functionality does not work as expected" because (...drum roll...) "the Visual Basic for Applications component is not activated unless you've previously activated one of the Macro commands on the Tools menu.". Workaround: Press ALT+F8 or ALT+F11 and restart Outlook.

Now - and this isn't supported by the KBA - what if, subject to thread contention/processor temperature/Mariner batting average/etc sometimes when Outlook boots it fires the Application_Startup event <span style="background-color: #FFFF00; color: #000000; font-weight: bold">before </span hi> the VBA component activation has completed: our attempt to catch the event would never get fired! This might explain why the problem is intermittent on many machines, and never seen on others.