by Jason Caldwell » October 8th, 2011, 10:16 pm
Thanks for the heads up on this thread.
Unfortunately, the PayPal Sandbox is under constant development, and thus, you are likely to see errors like this from time to time as they make changes/improvements to their system. I would try your test against a live account. If the problem continues, let's take a look at the page where your PayPal Button is presented ( please post a link if you can ), and we'll take a closer look. Your Shortcode looks good, so I suspect this is a Sandbox issue only.
Also, try clearing your browser's cache/temp files, and cookies as well. I've also seen weird things like this happen whenever you log in and out of both live/Sandbox accounts at PayPal. They seem to have some conflicts in the way cookies are stored in these two environments. This cookie issue/conflict between live and Sandbox accounts has been reported multiple times to PayPal, but it still lingers under the right circumstance it seems.