So we know that it's not the platform that makes a difference, how about this: what user interface are you guys running? I run UI2 with OpenGL but no alphablending.
I noticed that when a call comes in, the simplephone screen will briefly showup (less than a second) then dissapear. I can still hear the ringing of the phone on the MD, but don't see the phone. I then tried doing this while in KDE desktop, and went through all the open applications while the phone was ringing on the MD. The one that normally shows the phone is OrbiterGL, but in this case OrbiterGL only showed the Ui menu, but no phone screen (yet the phone was ringing).
So I believe that the problem is that the phone application is starting properly, just not showing up on the screen. This happens when I am watching TV, a video, or even playing music.
If I am doing nothing and just idle at the main screen, then the phone screen shows up and everything works as expected.
I noticed the same behavior on a tablet Orbiter (running UI1) that controls this MD. If the MD is running video, the orbiter does not show the phone screen when the phone rings. If the tablet Orbiter is at the main screen even though the MD is playing video (meaning I started the video via the tablet orbiter, then clicked on home on the tablet orbiter to get back to its main screen) then the phone is shown!
Any suggestions are welcome as usual...