I have a similar problem:
If I create 2 descriptor tabs, and then I go to the product page and then click on the second descriptor tab, and then try to add the product to the cart, I get the "Oops! An error has occurred. This error has been logged. If the problem persists, please contact us!" error, but when I check it isn't logged in the error log.
Does anyone know what the problem might be? I'm able to add the product to the cart if the first descriptor tab is selected.
Also, if I click Proceed to Checkout, I also get an error. This might be because I don't have any payment configurations set. The error is not logged either though.
More info: I'm running this on IIS7 on Vista. I'm using Visual Studio 2008 and Ajax Control Toolkit
Edit: nevermind, found solution here: http://dashcommerce.org/forums/p/269/1334.aspx#1334