Magento - Registration problem - User is sent to My Cart after entering billing information

When a user goes to checkout for their items, they are given the option to register. If that option is chosen, they proceed to enter their information. After entering their Billing Information and clicking Continue, they are sent back to the My Cart page and the registration process never completes. I attempted the fix located at the following SO question: Magento is redirecting to cart when continuing from Billing info - but it did not work.

Background info - I'm using a template designed for 1.4.x with Magento 1.5.0.1 stable. Here is the URL for my site:

http://allyourga.me

EDIT1: Errors deleted because they were unrelated

EDIT 2: This issue may be related to another one I'm having: Magento - Registration error - 1054 Unknown column 'ca.sort_order' in 'order clause'

Error logs from that question have been relisted below:

2011-04-19T23:04:43+00:00 ERR (3): Notice: Undefined index:  HTTP_USER_AGENT  in /home/user/public_html/app/design/frontend/base/theme100/template/page/ie/ie6.phtml on line 2
2011-04-19T23:04:43+00:00 ERR (3): Notice: Undefined index:  HTTP_开发者_开发问答USER_AGENT  in /home/user/public_html/app/design/frontend/base/theme100/template/page/ie/ie6.phtml on line 3
2011-04-19T23:04:43+00:00 ERR (3): Notice: Undefined index:  HTTP_USER_AGENT  in /home/user/public_html/app/design/frontend/base/theme100/template/page/ie/ie6.phtml on line 19
2011-04-19T23:04:43+00:00 ERR (3): Notice: Undefined index:  HTTP_USER_AGENT  in /home/user/public_html/app/design/frontend/base/theme100/template/page/ie/ie6.phtml on line 20

Lines 2, 3, 19, 20 from ie6.phhtml have been reproduced below:

2 if(eregi("opera",$_SERVER['HTTP_USER_AGENT'])) echo "<b></b>"; 
3 else if(eregi("MSIE 6.0",$_SERVER['HTTP_USER_AGENT'])) echo "

19 else if(eregi("Mozilla.[4.]",$_SERVER['HTTP_USER_AGENT'])) echo "<b></b>"; 
20 else if(eregi("Mozilla.[5|6]",$_SERVER['HTTP_USER_AGENT'])) echo "<b></b>"; 

EDIT 3: The errors posted from EDIT 2 are the ones that are related to this problem.

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The error in your log points to an issue with your actual Paypal integration. My first guess here would be that you entered incorrect/incomplete details for the Paypal configuration.

In fact, Paypal says:

This error can be caused by an incorrect API username, an incorrect API password, or an invalid API signature. Make sure that all three of these values are correct. For your security, PayPal does not report exactly which of these three values might be in error

Check your credentials and try again. Hope that helps!

Thanks, Joe .

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The problem was that I had a seriously defective database. I suspect the problem might have arisen either when uploading sample data from a purchased Magento template or when I was migrating my website from one server to a new one.

I fixed it by running Magento's database repair tool which can be found at the following link: http://www.magentocommerce.com/wiki/1_-_installation_and_configuration/db-repair-tool

The errors that popped up were a lot of Added missing foreign key(s) and two Added missing fields. For a full report on the errors that popped up, go to the following Stack Overflow question:

Magento - Database repair tool - Added missing foreign keys problems

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Although its old post but i want to share my experience. i was also facing this issue and then in net tab of firebug when i click continue after giving the billing information, there was 500 error. more investigation into the error log of magento shows its actually php-mcrypt was missing on vps. and i just installed n its working fine now. may this info help someone.