Web to Lead Problems

We have multiple sites. With the new implemetation, we now have to have a different form created for each site. We have noticed that after setting up a form, and seeing that it captures the lead correctly....that later, it appears to go thru the motions and lands on the return URL....but the lead does not show up in the CRM. This is using a newly generated form, that we had at one time confirmed worked properly. So what is going on - anyone else notice this..