After our organization updated to the latest version of CiviCRM, our users started receiving the following error after registering for events on our website:

> **Sorry but we are not able to provide this at the moment.**
> 
> Could not find valid value for id
> 
> Return to home page.

The user is properly registered on our system and receives a confirmation email.  It seems to be a problem with the thank you screen.  The configuration of the thank you screen is the same as before.

Ideas?