[development] Users can't log in after creation

["Schultz Consult - [René Madsen]"]

Hi,

Im having the following senario on a production site with drupal 4.6

1 User creates an account
2 user get his e-mail with password
3 User tries to log in, but get's a user not found

What is the problem. If the user waits 5-10 minuts, the user is able to 
log in.

Any ideas? slow database?

-- 
Best Regards
René Madsen
http://rene.schultzconsult.dk