Facebook/Mountain Lion incompatibility

There are so many people having problems with FaceTime and Messages that I decided to add my experience to perhaps move the ball a little. I have successfully used FaceTime from my iMac under Snow Leopard and from my iPad. I am still able to use them that way because I have Snow Leopard (SL) installed on an external disk and can start up from that disk. I am not able to use FaceTime under my recently installed Mountain Lion (ML). The problem is the same as everyone else’s, an error message telling me to check my internet connection. It works under SL but not under ML. Same hardware, same internet settings. I have tried all of the suggestions offered on the various threads including reinstalling ML. Nothing has worked so far in spite of the fact the experts are doing the best they can. So, the problem lies either with ML or the apps. Since two apps are experiencing the same problem, that indicates to me the problem lies with ML. If that’s the case, the problem can only be solved by Apple in a future version. It would be interesting to hear from users who have been successful using FaceTime under ML.