Cart checkout error...

[rpollard001]

Hi,

I have spent a multitude of hours trying to successfully upgrade Magento 1.11 to 1.12. This has been a nightmare and it shouldn't be.

What I have done:
1. Created a new folder inside the 1.11 web root called magento112 and unpacked the Magento 1.12 web root into it.
2. Per Magento Upgrading document, tarred and untarred the following folders from the 1.11 web root into the new magento112 web root:
app/design/frontend
skin/frontend
app/code/local
app/code/community
media/
3. rsynced from the old 1.11 web root the rest of the files using:
rsync -vr --ignore-existing <1.11 source web root> <1.12 target web root>
4. Dropped a foreign key in the wishlist table to allow the Magento database upgrade to complete successfully
5. Change base url
6. Connected through the web interface to magento112 web root like http : // <IP of Host>/magento112/
7. Modified permissions on directory to all allow more open access to media, skin, var, etc.
8. Cleared cache
9. Rebuilt indexes through the command line using:
php shell/indexer.php --reindex all

Everything works up to the point where I try to Add to Cart and come up with the following error returned on the page:

Server error
The website encountered an error while retrieving http://194.3.15.235/checkout/cart/add/u ... duct/7904/. It may be down for maintenance or configured incorrectly.
Here are some suggestions:
Reload this webpage later.
HTTP Error 500 (Internal Server Error): An unexpected condition was encountered while the server was attempting to fulfill the request.

The Exception log gives this error:
2013-04-29T19:00:26+00:00 ERR (3): Strict Notice: Only variables should be passed by reference in /var/www/html/app/code/local/MageWorx/SeoSuite/Block/Page/Html/Head.php on line 180

Can anyone give a clue as to where to look or any background information as to where to start?

I appreciate any help you can give!

Update:

The errors in the system.log and exception.log I don't believe are relevant but this error in Apache's log is:
[Mon Apr 29 15:03:50 2013] [error] [client <client IP>] PHP Fatal error: Undefined class constant 'TYPE_BILLING' in /var/www/html/app/code/core/Mage/Sales/Model/Quote.php on line 547, referer: http : // <host name>/lindy-tournament-marker-buoy.html?options=cart

[edmondscommerce]

The error is clearly in your custom module:

MageWorx/SeoSuite

It looks like their code does not meet the strict standards.

Your options are either to contact them to get them to supply you with an updated module that passes this level of error checking (favourite)

Or fix the errors yourself

Or (least favourite) lower the error reporting level of PHP so it ignores strict errors
http://php.net/manual/en/function.error-reporting.php