I was facing this error after revolution upgrade from 2.0 to 2.1.5-pl. I gone through forums but didnt found proper solution may be i missed something.
I got it solved myself, by rerunning setup again. One more thing i want to mention that i have set 777 for all the directories. It was on my local machine so i am not caring about security, but if you are applying this on live server then please apply 777 to only recommended directories and not to all.
So the conclusion is : Running setup again with proper directory permissions can solve this issue.
[ed. note: amitpatil last edited this post 14 years, 10 months ago.]