PayPal Cert Problem
It was brought to my attention tonight that my PayPal certs expired for all purchase and donation links on my site. Apparently, this has been a problem since March 20th or so. The problem has been fixed.
(I had wrongly assumed that PayPal might notify me of the impending expiration.)
If you tried to purchase PostCheck or make a donation to the Google Maps Plugin and ran into the error, I apologize for the inconvenience.