Currently Avast is throwing a false positive error when you try to pay with Paypal. Information about it is here: https://forum.avast.com/index.php?topic=220385.0

Work around is to sign into Paypal first (from their webpage), then click on the Pay button at Rendo. Otherwise Avast will terminate the connection and give you a really scary error message. It's happening over at DAZ also. Other Anti-Virus programs aren't affected.

Thank you for the information! I will let our programmers know.