This error comes when i click proceed to check out. plz any one help me... In that folder there is no code behind files how i will debugging

In the admin section you can look at the error message

You are using the Web Ready version that is compiled so to debug you have to have the source version

I am getting this same error attempting to Check Out with PayPal.  The error IS NOT appearing in the admin error logs section.  I have configured my API.

 Two things to look for on this that I found. 1st this error if are receiving it on the return from PayPal while using the sandbox (test environment) doesn't always work quite as well as the live version. What I've found is for whatever reason in the sandbox environment I've noticed the properties being returned are not always correct. Hence you get a typical "Object reference" promblem. Simply put DC is expecting something that is not being delivered by PayPal. 

 Live PayPal seems to be more stable and works just fine. I had this issue last night as I was working with this myself. I also found that if you do not pay attention to how you are setting up your provider you can make a mistake there quite easily. 

 Make sure you have the correct default provider setup and enabled. Also pay attention the difference between the std. paypal provider and the pro in that the fields required are different (obviously that is evident but in clicking the pages quickly while troubleshooting I caught myself puttting in the Pro API string into the PDT ID as they are similar. Setting up the PDT ID in the sandbox was not as direct as you might think. In fact the pre config. PayPal accounts default to the Pro API. You have to login to the account and setup through the "profile" tab and then the "Web Payments" configuration page.

 Hope that gives you a hand.

I get the same error when clicking on site settings under the site menu. This only happens on the host server and not on my local computer. I thought it was related to the tabs and ajax, but I'm told they have the latest AJAX installs. Anyone have an idea? And actually, can I get any more detailed error messages? Also, nothing is showing up in the error logs. After I turned off the customError, I get the following. I'm new to both dashCommerce and .Net. Any help would be appreciated. Thanks in advance.

Line 21:       <dashCommerce:CacheSettings ID="dcCachingSettings" runat="server" />
Line 22:       <dashCommerce:Analytics ID="dcAnalytics" runat="server" />
Line 23:       <dashCommerce:Images ID="dcImagesSettings" runat="server" />
Line 24:       <dashCommerce:SeoSettings ID="dcSeoSettings" runat="server" />
Line 25:     </div>

Just to update you guys, it looks like a couple of files were 0 bytes as a result of ftp'ing them to my host. Re-copied the files and everything works great! By the way, great product! Thanks!