OSX Messages shows contact accounts as invalid I had Messages.app when I got my mac a year and a half ago and it worked great.

However, since a few weeks ago all my contacts in my previous conversations appear in red (as if they do not have an account). 

What's even more curious is that I can see when people are actually typing (I see the 3 dots (dis)appearing), but I only get the message on my iDevices. 

Solutions I have already tried : 


Restarting messages
Signing out/in my account
Rebooting


I am now out of solutions, do you guy have any ideas what the problem might be?

NB : My OSX is up-to-date with 10.9.3

Edit : It also doesn't work on my iPad (iPhone is still OK, receiving iMessages as iMessages).
Edit2:  I hoped updating to Yosemite would help. But no :(
It's only a guess, but your scenario matches an issue I had with my iDevices and Message on the Mac too. See also the discussion here.

What resolved the issue was activating the iMessage Setting on my iPhone via Settings &gt; Messages.

Strangely this does effect the Messages send/receive on the Mac as well!

Can you verify this?