Ok, so I've made some headway on this. Hopefully it will help some others on the same path. The real problem is not the crossdomain.xml, it had to do with the URI of the WSDL being an HTTPS and the site it was requesting the HTTPS from did not have a legitamate SSL certificate. I tried downloading the self signed certificate and importing it into a keystore in JRE and also FlashBuilder's JRE. Other's have found a solution that way, but I have not gotten FlashBuilder to successfully accept it even with the imported certificate.
However, I did find a solution for those who are trying to import the Portabilling WSDL who are having the same problem with the SSL. All I had to do was to import the WSDL into FlashBuilder / Flex through the URI of https://demo.portaone.com/wsdl/<whatever WSDL extension>. This had a legitimate SSL and imported with no need for a crossdomain.xml. After the Flex code was generated through the importing process I just went in and changed the URIs back to the domain that I was working with, and Viola! I ran a login test and it was successful.
I tried to solve this problem too.
I changed the cacerts file for JRE Flash Builder 4, and it worked - it could read the wsdl file, and FB created all of the objects.