Same here… I have tried to found solutions about two weeks for now.... still nothing.
I started to get same error on three diffrent websites… all of them are in diffrend servers. Also before i started to get this error i did not change any of the file or something like that.
i found the problem. It have somekind of virus on the webpage have been hacked. There is some new catalogues and files what make this. Don’t know how it have been get in tehre… so it must be some Magento security hole.
So try to found from the catalogues:
It is in you root but also i found from inside of many other catalogues.
And then there was another catalogue what have named with some number… As i run three Magento sites.. .they all have this cataloge named with diffrent number. So you should also delete this catalogue.
Just in case you should first download those catalogues to your computer so that if you delete wrong thing you can upload it back.
If someone know hoy those bad files suddenly come there then i will like to know it to fix that security hole.