Problem with Payment Gem

I have a shopping cart app (yes, another one) that uses the Payment gem
to perform credit card authorizations with Authorize.net. I have
created and submitted transactions using their test card numbers and
received responsed from Authorize. The problem I am having is that
regardless of whether the transaction is approved/denied (based on the
returned codes and message) the “transaction.submit” raises an exception
in my controller. I have used “transaction.inspect” to review the
submitted transaction and all seems well, but there are many different
fields/flags that may or may not be set correctly. I am working in test
mode with my Authorize.net account, but changing it did not seem to make
a difference. Has anyone else experienced this and are there
suggestions for resolving it?

Thanks,
Nathan