While this thread is almost a year old, there is a periodic error message now arising that says this which will quite often disappear if you try again later. For good measure, log out and clear your cache or browser history and restart your computer before making subsequent attempts.
But yes, early adopters (sellers) of the new ebay payment gateway are not eligible to collect funds via paypal anymore. That is also a possibility.
When this happened to me as a buyer, however, the error vanished with my next attempt.
