[TYPO3-english] direct mail and cron

[Piers temp account]

I'm having problems setting up the cron job in direct mail. I set up  
the cron job fine, but it returns the error

Failed opening required '//t3lib/ 
class.t3lib_div.php' (include_path='.:/usr/lib/php:/usr/local/lib/ 
php') in /home/wwwcity/public_html/typo3conf/ext/direct_mail/res/ 
scripts/dmailerd.phpcron on line 61

which makes me think it's not generating the path to the file properly  
in dmailerd.phpcron.

I could hard-code a path in this file, but I can't edit the file from  
typo3 or upload an amended one because I don't have the permissions.

This is the real problem, I don't know how to edit the file, and I'm a  
php person rather than a unix person.

Any help would be greatly appreciated, I don't know if others have had  
experiences with editing files in extensions that they're not supposed  
to?

Thanks,

Piers Aitman