I am the person who created the page with the Camptix plugin, and am the only one out of 3 people who tested the page that received this error message. That leads me to believe there was an issue with my Paypal account's linked bank account, or something, but that does not appear to be the case.
When I run the transaction through my cc (without paypal), it goes through fine, so at least I know to focus on my paypal account...from what I can tell, since the other's transactions went through fine, there is only an issue on my side.
Any suggestions?