Hi guys, I'm following all the steps to transfer my store to another host and it doesn't seem to work for me!

I installed a whole new zen cart, I've exported my OLD database tables and imported them to the new host and uploaded all the files from my OLD host except the config files and it doesn't seem to work! I get

HTTP Error 500 (Internal Server Error): An unexpected condition was encountered while the server was attempting to fulfill the request.

i check the debug log and this is what I get:
[09-Aug-2012 05:38:48 UTC] PHP Fatal error: Cannot redeclare date_diff() in /home/content/69/9720269/html/store/includes/functions/functions_general.php on line 2951

and the other one says
[09-Aug-2012 05:38:06 UTC] PHP Fatal error: Cannot redeclare date_diff() in /home/content/69/9720269/html/store/velutto/includes/functions/general.php on line 6001

can someone please help me? I've uninstalled and installed zen cart twice already. I'm ready for someone else to just do it for me, I'll pay. I'm frustrated!

Thank you guys!