I installed OPC and now I'm unable to checkout. So here's what's happening, when I click on "Place Order", the button gets disabled and the page goes nowhere. There is no order saved and the cart is still full.
I checked this in Firefox using the Console and everything happens fine, but it gets stuck at POST http://www.mywebsite.com/onepage/json/saveOrder [HTTP/1.1 500 Internal Server Error 1340ms]
I tried increasing the Memory size to 256M in php.ini, but it still isn't working. Please help. Also disabled all third party extensions.