Hello Rene. I have the same problem like prasannjeet, but my is a bit strange.
Your solution doesn’t helped so I first deactived the plugin but there was still the same problem. Then I deleted the whole plugin but now I STILL have this error message!
I am totally confused now. I would love to get a hint to resolve this problem.
BTW: The problem came with the transfer to a new webserver.
Update: Problem solved!