I have a web site with a shopping cart that also connects to PayPal if
the customer wishes to do this our cart can only accept Visa and MC
PayPal of course accepts more cards + e cheque. Hence the two payment
processors. There are some difficulties transferring infor from our cart
to PayPal and requires customers to enter their info again. This is a
pain. What is forseen as a problem or a solution is having two shopping carts one
ours, one say PayPal. Instead of after once inputing their info then
choosing a payment processor as above. They first choose a payment
processor which takes you to one of the above carts. Yes it is
duplication, two carts, but I think it is simpler for the customer,
what do you think and what might the problems be. Double the work to
update obviously, what else, rating? What?

What kind of shopping cart software do you use? You are aware of the
problem with your current choice of shopping cart, have you had a look
at other solutions that might eliminate the problem you are having?

http://www.oscommerce.com/ is a well known free shopping cart software
that works nicely.
more options here ://www.google.com/search?q=free+online+shopping+cart+software&btnG=Search&hl=en&lr=