Something I noticed related to this:
Sometimes you will get the "The following message could not be delivered to all recipients" message while the message actually DOES get delivered. I noticed this when I was re-sending a message because I got the warning message. My contact started to complain why I said that line twice.
But on the other hand... MUCH more irritating� Sometimes you DON'T get the "The following message could not be delivered to all recipients" warning and the message still doesn't get send

. I had this at least twice, ask segosa

.
As far as I can tell these errors aren't caused by connection problems on the user's side. At least not every time I encountered them.
It does look like this kind of errors started to occur more since WLM testing started.... I see this kind of errors way more now then I used to see them like a half year ago. This is what Fanta meant too, I think.