Since I have updated to OSX 10.8 Mountain Lion, I am experiencing a series of issues with the notifications from Messages app, in particular when receiving new messages through the iMessage service.

Here is what happens:

When I receive messages through iMessage on OS X 10.8, the banner notifications and the concomitant sounds are only displayed for the first incoming messages that start a new conversation. By "new conversations", I mean those which are not already in the left-side panel of the main Messages window. Of course, the app must be in the background to display any notification at all.

But then, when the user activates the in order to reply to the messages received, and then deactivates the app, any new message that arrives in an open conversation will not play any sound, nor will it show any notification banner. Messages app becomes mute until the user deliberately close (CMD-SHIFT-W) such open conversation. Only then, any new message will show a banner and play a sound... until again the user activates the Messages app, and the cycle starts over.

The dock icon's badge with the unread count gets silently updated in both cases -- although this is not enough for those like me who prefer to keep the Dock hidden.

When using all the other IM services (except iMessage), however, the notification banners and the sounds are triggered correctly as usual. By "correctly", I mean that whenever the is in the background, a notification is shown both in the up-right corner and in the Notification Center, the "new message" sound is played, and the dock-badge count is updated.

The issue then occurs only when using iMessage, and does not occur with the other IM services, making iMessage's behaviour utterly inconsistent with the behaviour of the other services within the same application.

There is also another issue that similarly only occurs with iMessage and not with other chat services.

When the is closed and a new iMessage is received, then the app opens itself in the background -- so far so good -- but then no sound is played nor no banner is displayed: again, only the dock badge is updated. And this occurs only for the very first message when the application is closed and opens automatically. And it occurs whether or not the message belongs to an already open conversation or if it starts a new one.

Sadly, OS X 10.8.1 update did not fix these issues -- nor, as far as I can tell, the 10.8.2 developer beta (build 12C31a).

I am an enthusiast early adopter of iMessage on both the iPhone and the Mac, and have encouraged many others to join. But after Mountain Lion's release, I feel that the got even worse than the beta.

I can't rely on a messaging application which does not notify me _consistently_ when I receive a new incoming message!

has anybody here also experienced this issue?
Let me know in case you find any workaround.