Clicking on buy button brings the user back to checkout page

This is happening with my store as well. No transactions can go through. User hits purchased and it just goes back to top of the page. I reverted back to WP 3.6.1 and its still doing it
http://turqsport.com although i may have to put up an under construction block

Thanks Varktech. I was thinking its something with too many scripts being called so i was trying to configure BWP-minify and now WP Total Cache but auto minify is too much and breaks things too. ackkkk.

determined that people had to be logged in or it would fail. now i need to figure out guest check out

@gretarmagg
The place to start is in Chrome or Firefox with Firebug, and checking for JS errors…

@gretarmagg & @nurenu
Assuming that the problem may be a conflict, a help would be to use the deactivate dance –
deactivate all plugins but wpec, switch to the 2012 theme, test. If clear, add 1 plugin or the theme, retest. Rinse and repeat until you’ve identified the errant module.