Ok thanks i think that has worked now. I can now create a user from the backend which i couldnt before.
Although now when i click on most of the menu links, like view stores, or seller profiles, in front end i get the following message
"Cache storage database not found for products. You may need to rebuild the cache first."
I have hit the cache button in Sellacious backend and cleared joomla cache but its not fixed it.
Thanks.