Sîngeorzan Cristina 

Can you click on the small disk, save the XML file to your desktop, and then attach that same file to your next reply.  That may contain information that helps with finding a solution to your problem:

Thank you for your reply. I've only received the error once today, and as much as I've tried to recreate it I couldn't. But I've discovered something else. I've almost forgotten that I installed Vertical Review, and after uninstalling it, the problem was gone. I think this was the problem. I have looked up and found a solution you provided to another user and you mentioned the apps (I haven't thought about them to be honest). Once again, thank you for your reply and the solutions you provide. Have a nice day!

Thank you for your reply. I've only received the error once today, and as much as I've tried to recreate it I couldn't. But I've discovered something else. I've almost forgotten that I installed Vertical Review, and after uninstalling it, the problem was gone. I think this was the problem. I have looked up and found a solution you provided to another user and you mentioned the apps (I haven't thought about them to be honest). Once again, thank you for your reply and the solutions you provide. Have a nice day!

Sîngeorzan Cristina 

Great... thanks for confirming.  Maybe Oana Nagy can test that theory with the Vertical Review so the developer can issue a fix if needed.