I personnally tested my urls on the claim form and it worked.
If you are getting a 404 error it could be that your url is made up.
All instawallet urls that have received transactions are in the database.
Boussac (Pierre) you come back after ignoring questions and the first thing you say to a guy who has lost a shedload if coins is that maybe his URL is made up.
Way to go mate. Good job.