hikashop registration failed

I have the above problem, sometimes everything works fine when i submit the registration it send back an email but most times its gives the above message
42 - Failed to update contact: COM_CONTACT_ERROR_UNIQUE_ALIAS
You may not be able to visit this page because of:

an out-of-date bookmark/favourite
a search engine that has an out-of-date listing for this site
a mistyped address
you have no access to this page
The requested resource was not found.
An error has occurred while processing your request.
Please try one of the following pages:

Home Page
If difficulties persist, please contact the System Administrator of this site and report the error below..

my site is www.jepeto-handmade.gr
i dont know what to do

sorry it seems that the Contactcreator from Joomla was still activated under plugins. After deactivation it all worked fine.

Glad to know that you found out what your problem was .