I had a problem with seeing "Sorry, site is unavailable now, please try again later." after posting in the forums at times, but not in every message and it didn't depend on the message length so after a bit of searching both here on Unity and in the database I discovered the sometimes when a message is copied and pasted into the forum it ends up with a paragraph return code that looks something like the ascii code #158 that Orca doesn't understand but shows up clearly in notepad.
In my case this code caused the "Sorry, site is unavailable now, please try again later" error.
