Okay it happened again - I looked at a thread - hit the back button and got the following:

vBulletin Message

Sorry-no matches. Please try some different terms.

The above line was in a box - here is the url (if it is of any use)
http://www.flyertalk.com/forum/searc...4&pp=25&page=2

don't know if this helps - but I had more than one window open with FT - when I went back and went to forums and then new posts on the page that had given me the error messsage it said my last visit was at 5:02 (the error happened about 5:58) and there were 110 results of search (eg new posts)
where previously it had been over 200 or so. Something is being reset but I don't know how or why