I checked all the PM settings several times and everything should be OK - as far as I can see I have no "privacy" settings activated.

It's a long shot, but could the signature be a problem? Many years ago I remember had to choose another signature in some login process - "cls" was a reserved word and wasn't approved as a signature. (Those of us who had computers long ago without any windows whatsoever recognize the signature as an acronym for "clear screen".)