I have installed a fresh copy of phpbb seo two days back on my domain and here is the url -http://www.snbc.co.in/careeradvice/index.php. if i try to post a thread related to search engine optimization the thread's not being posted. instead, it is showing 404 page.But if i edit and put any other word instead of search engine optimization it is working fine.Even it is working for the word search engine optimisation ("s") when spelled incorrectly.I checked if there is a problem with phpbb seo mod i even installed a copy from phpbb.com but the problem remains the same.Not only phpbb it is the same with any forum software i use.

Well, this is strange, but it does not come from our code : http://demo.phpbb-seo.net/demo-en/searc ... n-t55.html

Did you published the article, otherwise it will show 404 if you just published it offline. Most 404 issues are certainly from the page that is not yet active if it was not deleted.