I'm experiencing the same problem, but memory is not my issue. When I turn on the debugging the "Proceed the Checkout" Link goes to a blank page so I can't give you a screenshot, otherwise it says:
The website encountered an error while retrieving
bearstitches.com/new/index.php/component...type-cart?Itemid=102
. 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.
site is here
http://bearstitches.com/new/