Thanks for that.

I looked at the cache folder, got this

[16-May-2012 18:16:53 UTC] PHP Fatal error: Call to undefined function tep_db_query() in /customers/3/f/d/scrapbookparty.co.uk/httpd.www/includes/modules/payment/authorizenet_cc_aim.php on line 273

so is this saying the error is in the authorizenet_cc_aim.php file?

I dont want to use authorize.net so would deleting the .php file 'fix' it?