AbleCommerce Shopping Cart Software

I found this post: viewtopic.php?f=44&t=9620 , and while replacing OnePageCheckout.* didn't help, replacing App_Code/CheckoutEvent.cs resolved the issue. I still don't know why this happened, however.

I started getting this error today. OnePageCheckout hasn't been altered since the site launched in June, so I don' t know why I'm getting this error. Please help! Details: [[ConLib:OnePageCheckout EnableGiftWrap="False" EnableShipMessage="True" MaxCheckoutAttemptsPerMinute="20"]] c:\websites\AC702\C...