You should be able to download drivers and firmware from the smc site here.
Also see the FAQ or knowledge base articles to help you with installation questions.
A great site for help with all sorts of broadband and or wireless issues is this one.
It takes a little reading to find the right section, perhaps, but a wealth of reliable info there. (You'll see there's an SMC forum, but read the FAQs too.)
I hope this information allows you to resolve this issue. If you need further assistance, please post back with a comment to this thread.
If I've managed to answer your question or solve a problem, please take just a moment to rate this post....thanks!