I just was getting this error:
Error has occured. Please contact your administrator.
This happened when under Site Content and Structure and viewing the Pages folder. At the same time, I was also in SharePoint Designer (SPD). I had just created 2 new pages based on a new page layout I was testing. I had to add another Tag Prefix to my Page Layout, so I "Detached" one of my new pages in SPD to compare Tags just as a test. All seemed to be fine, at the moment. When I went back into Site Content and Structure / Site / Pages, I got the "Error".
Apparently, SharePoint(in the web browser) didn't like the fact that I detached one of the pages from the page layout, so it wouldn't even list the pages in the folder. I had to delete the offending pages in SPD. After that, all is well.
I hope that this helps anyone else asking themselves "WTF? What did I do?". :)
