Urgent help needed: Paypal Issues

Getting error messages when trying to complete the transaction via paypal express!!

they look like...

Warning: Reset() [function.reset]: Passed variable is not an array or object in
/home/d1d10000/public_html/zencart/zen-cart/includes/modules/order_total/ot_group_pricing.php on line 77

Warning: Reset() [function.reset]: Passed variable is not an array or object in
/home/d1d10000/public_html/zencart/zen-cart/includes/modules/order_total/ot_group_pricing.php on line 78

Warning: Reset() [function.reset]: Passed variable is not an array or object in
/home/d1d10000/public_html/zencart/zen-cart/includes/modules/order_total/ot_tax.php on line 38

Warning: Reset() [function.reset]: Passed variable is not an array or object in
/home/d1d10000/public_html/zencart/zen-cart/includes/modules/order_total/ot_tax.php on line 39

Warning: Cannot modify header nformation - headers already sent by (output started at /home/d1d10000/public_html/zencart/zen-cart/includes/modules/order_total/ot_group_pricing.php:77) in /home/d1d10000/public_html/zencart/zen-cart/includes/functions/functions_general.php on line 44

what does all this mean? and how can i resolve this matter?!!?!

What version of Zen Cart?

The Latest version 1.3.7....

The error you're experiencing was fixed in v1.3.7.1.

You can either install v1.3.7.1: http://www.zen-cart.com/forum/showthread.php?t=69769
or install the latest PayPal patch which is included in v1.3.7.1: http://www.zen-cart.com/forum/showthread.php?t=56216

im in the process of re-applying the paypal settings... in the paypal IPN settings i belive that there should be a space for the "identity token" given from paypal... i dont seem to have a box which supports this in my admin section.... how do i get this identity token applied to the site?????

If the PDT option isn't listed then you've not installed the most current version of the patch as instructed in the thread I pointed you to, and/or you haven't removed and re-installed the module from the admin.