I have just upgraded to v1.5.5e, everything works apart from blank pages when I click on 'Checkout' or 'log-in', the pages are completely blank!!

I have spent a lot of time looking to find the issue, but without any luck! Hope you gurus can help!

The test site can be viewed here: http://mlfencing.com/zencart139/

What could have caused this? I am running php5.6

Big thanks in advance!!!!