Joomla site server transfer - mysql error ?

Hi.
i am trying to transfer a Joomla site from one server to another. the site works perfectly where it is but when transferred i get a db error when i try and login to the site. this identical error comes up in several places but always when trying to login or register on the site:

Fatal error: Cannot redeclare JTableUser::$barcard in /home/ginger/public_html/royalnorthdevongolfclub/libraries/joomla/database/table/user.php on line 118

I have backed up the site numerous times in different ways and used Joomlapack to restore the db aswell as trying a manual export and import, always i get the same fault.

The reference to barcard in the fault makes me think this might have been to do with a few months ago i edited the sites code and db to allow for an extra field in the registration, i just followed some online instructions and it worked perfectly. however it may be this causing the problem now, is there a possibility this part of the db isnt exporting properly ? my mysql knowledge is zero really so i am hopeing for a little help with what probably is a simple issue to someone who knows !

many thanks in advance.

the site is at www.royalnorthdevongolfclub.co.uk