I'm not quite sure what the problem is but it seems like the program doesn't like certain types of urls. I had a similar problem today posting a link. It would accept it if I did it one way but not if I did it a different way. You can see what I mean in the last two lines of
viewtopic.php?f=21&t=1389 The two article links have different styles because I got an error message if I did the second link the same way I did the first link. The computer was happy if I did it a different way.
phpbb comes out with program updates periodically and I ran the latest update last night. I wonder if there was a glitch in the update because I never had this problem before. If so, it'll eventually get fixed. In the meantime we just have to work around it the best we can.