View Accounts Not Working

Hello
I have a strange problem, that seems to have happened out of the blue.
When I (or any users) click on the 'my account' link it takes you to the correct page, but no information is displayed.
The 'view', 'edit', 'delete' tabs are still showing.
When clicking on the edit tab all the information is present and working.
Unfortunately Iam unable to view any of the accounts, including my own.
I have absolutely no idea why this has started happening.
Any advice / help would be much appriciated.
Thanks in advance :)