I finally got around to signing up for a Paypal sandbox account, so I can test my E-Commerce setup, specifically shopping cart transactions - without charging a million $1 to my personal Paypal account and then refunding them from my business account.
I signed up for Paypal sandbox at developer.paypal.com, got my login info, and setup a buyer and seller account. In my shopping cart (Ubercart - good stuff, and it's free :), I set the Paypal settings to "Sandbox."
My problem is that whenever I make a test (sandbox) purchase, I get taken to the Paypal website and see an "Internal Server Error." Any ideas what I might have missed here?