There are tomes on the web about this failed feature. HOWEVER there are network settings we always need to check. I noted it in the CNET Networking Forum at this link:
http://forums.cnet.com/7726-7589_102-5412417.html?tag=posts;msg5412417

Remember due to changes by Sam, Apple and more, this feature is hit and miss. Apple and Sam don't have a good relationship to boot.
Bob