Okay, as I got now my 10000 hoorays I open up the Pandora box

Yep, for some it was working fine, for others not!
Up to now no one (I know of) had a clue why. Even 'rumors' about IMEI databases, blocking by operator on purpose, ...
But it is all due to my operator(s) decided to send MMS according to specification 1.1 (fmms sends and receives only 1.0). So the header parsing went berserk and screwed everything.

This fix only adds one specific 1.1 header (X-MMS-Retrieve-Status), but that was sufficient for me (there are of course more and even spec.1.2).
So what I would like to get is some feedback from users who suffered non-ability-of-receiving.
[i.e. for you it does not matter atm and NO it will NOT break anything]

--
edit to misiak's edit
Yes that is the layout code of the message. And should not be in the message text itself. You are lucky that the text of message (or was it subject?) seems to be in front of smil info. Other way round message would have been unreadable possibly. And I assume that some length has not been read correct or text was not-Null terminated (which is only normal at the end) or some special characters (unicode?) screwed it up.
But as you say only a few are borked.
And no I am sure my fix has nothing to do with it.