PHP Fatal error: Call to a member function credit_selection()

[ajmn]

error log:

[01-Jun-2012 14:56:38] PHP Fatal error: Call to a member function credit_selection() on a non-object in /var/www/vhosts/mydomain.co.uk/httpdocs/mystore/includes/templates/mytemplate/templates/tpl_modules_shipping_estimator.php on line 187

i seem to have a few of these messages all identical (except the time and date!)
also there seem to be many created on each occasion <-- all identical bar the logged at seconds
eg

[13-May-2012 00:36:24]....php on line 187
[13-May-2012 00:36:17]....php on line 187
[13-May-2012 00:36:07]....php on line 187

you can see from the gif image that on 13May and 5 May many were created in a short space of time, and yet on other days only a few were created



i've looked at the mentioned file, the line numbers only go to 164, so i'm a little confused!

any clues to how to track the problem down and fix ???


EDIT: :) mm, pretty pointless attaching a picture file if the forum software 1. reduces it in size to be unviewable and 2. changes the format from gif to jpg !