Open up system preferences and go to network. Make a note of your settings as you may have to rebuild them.
Click on finder
On the top meny bar select Go and under that option "Go to Folder"
put the following in .... /Library/Preferences/SystemConfiguration/
Rename the preferences.plist file that you see in the window, to preferences.plist.old
Reboot your mac - a new preferences.plist file will be generated. This step is important
Check your network settings and make them the same as before if required.
That should help.
By the way - all this information was supplied by a user called James_N from this link...
https://discussions.apple.com/thread/3200535?start=0&tstart=0
I've just made it simplier to follow 🙂