I am using 1.3.8a and at the moment don't have time to do the testing to move to 1.3.9. However we are using Netbanx payment module which has been supplied by Netbanx. If used properly there is no issue but if you process an order successfully and then try to process a second with an error or by cancelling from Netbanx it then reports a successful transaction.

Netbanx say that this is a known problem with Zen Cart. They say "This is unfortunately an issue with Zen Cart's own session keeping"

Is there a fix for this please?