New Smartview log in issue: Excel and Outlook become unresponsive

Over the last week I have been experiencing a new, intermittent problem when logging in to EPM Planning, Freeform & Narrative applications through SmartView in Excel.

After providing user credentials via SSO in the browser pop up, I see a 'processing XML' window which continues to display, but nothing further happens and Excel becomes unresponsive. While this is happening I am also unable to select and switch to a previously opened Outlook application window. Only solution is to force Excel shutdown.

Problem is not consistent. Some times it works, some times it doesn't, but haven't been able to isolate a specific circumstance.