Internet sharing in Mountain Lion not working (sharing ethernet from MBP over Wifi)

I just updated my parents iMac to ML and are experiencing the same issues although I have sporadically connected. I have tried changing network name, channel, open and secure, restarting all devices etc. I even tried sharing the network through iPhone USB, but it didn't work. I once got it working on one iPhone 3G and a MBA, but not the 4S at the same time. Then I got it working only the MBA, then on nothing, then ad hoc on units, but only for a short period.

The error messages are mainly (loosely translated)

• "Could not connect to network …"
• "Connection timed out"

(…and it doesn't seem like discussions.apple.com is maintaining HTML markup although providing an advanced text editor…)

BTW: I think have posted this in the wrong forum.

I had the same problem, and I think I have fixed it. What was happening for me was everything was running just fine until I had to restart my Mac for whatever reason and then my iPad and iPhone both stopped being able to connect to the Internet although they were connected to the shared network I had created.

To get it working again all I had to do was go into General settings on the iThings and go to reset and select 'Reset Network Settings' (The downside of this, of course, is that it will forget all your other passwords.) and then I was able to reconnect.

I also discovered in the Keychain Access on the Mac that there were several versions of the Internet Sharing password stored in there from when I had messed about changing the network name and such like, so I deleted all of those and set a new password for the network.

Hope this is of some use to you.

I have an issue on ML with internet sharing.

ethernet works fine and wifi works fine.

I go to share ethernet over wifi and i push start in interent sharing and wifi turns itself off. its like it fails to start and shuts off

internet sharing is checked and on and I can go turn wifi back on and use wifi again while internet sharing is on but if I turn off internet sharing and then try to start it again wifi just shuts off.

please help if you know a solution

For all the people who have enabled internet sharing via wi-fi and yet not able to get your decives to connect via wi-fi to your Mac please check your Firewall settings on your Mac.

Go to settings > security and privacy > firewall tab > do a switch off firwall and save

But those who want the firewall and yet only allow local internet sharing, turn firewall on (which would be on by default since your internet sharing wasn't working), click firewall options, uncheck "block all incoming connections"