Board Thread:Questions and Answers/@comment-26214638-20151208193927/@comment-26828130-20151210185905

You were;
 * 1) Clicking on a link that was generated by Mr. Bill (from the popup you see when clicking trains at his station), the invalid error happens alot on those posts
 * 2) Clicking a link from a new neighbor, links posted BEFORE you became friends give the invalid error
 * 3) Clicking a link from a non-neighbor, if one of your friends liked a post of one of his neighbors, that isn't your neighbor

These are the things i know of that give te error, but i think the TS Forum is a better place to ask