[SOLVED] Shopping cart won't hold items

I set up a test instance of 1.5.0.5, but do not have mail() working on this machine, so accounts might not be fully set up properly. I did approve accounts on the admin side.

When adding items to cart (when logged in), opencart says something has been added to cart, but nothing is added. Even if I click logout, still can't add to shopping cart. (I seem to have been able to add something to cart at some point today, before logging in.)

What can I do to fix or work around this? Can I disable the need for email account validation/announcement? Can I change anything in the db to make these accounts work with accounts?

Cookie issue?

I found the reason: weight_class_id was not set correctly for the products (there were some that were right which is why sporadically it would work for me).