Issue with Google Webmaster Tool

Guys, have this ever happened to you?

Suddenly this error pops up and any idea how to fix this? Seems like the issue is due to the ‘/’ symbol in general.

Suggestions? I can’t seem to find the cause of it. Using Yoast SEO..

Please advise and sorry for disturbing!

Link to the image: http://www.flickr.com/photos/nicregi/11293030973