Out of Office stopped working with Outlook 2013

A few days ago we noticed that people using Outlook 2013 could no longer access their out of office. Everyone using 2010 or 2007 can still use it.  We are running exchange 2007.

The problem isn't with the mailboxes as on older versions of office they can use OOF. They can also use OOF in OWA. 

As OOF was working I'm wondering if this is a bug with a windows update? I've checked autodiscover is working, and it's not being stopped by our proxy.

If anyone could shed any light on this I'd be really grateful. 

Thanks