|so what your saying is that you both have the CD code? as well as a version problem? well you need to make sure you updated both versions of the game, this meaning you need to make sure you download the patchs from the recommended sites (try the home page), as for the code? you will need to get one from another source im afriad :) wether leagal or illiagal just be careful, plus most games are not backwards compatable with there unexpanded selfs.|
so, get another key (always worth it)
Make sure he has the same version as you, either patched or got the expansion.
and if you have LAN problems restart your router, refresh your network, and clean any contacts, if you also have software LAN issues make sure windows is updated (if you use windows) and you have run the "Network Connection Wizard"
other than that i have no idea, hope you sort it.