I too am having this issue.
What version of Tableau Server are you using ?
And has it been since maybe going to 7.0.1 ?
I should have also added that 'viewing' the workbooks via the web is not a problem.
Message was edited by: Justyn Attwool simple message about viewing.
Ok the Tableau Server issue has gone since doing a Stop and Start of tableau server.
Can't say if that's the ultimate fix - as I also removed a worker node.