Form submittion redirected with 302 "Moved Permanently" response, Form Post Failed !!!

I've got a page which does a form submit which executes successfully when i click  the submit in the first time. then if i change the field again and submit. The  page gets a 302 status and redirects to same URL losing its post data. this make  the submit to fail updating field data to database.  anyone got any idea , what is going wrong !!!!