serendipity, do you or your contacts, by any chance, use the word filtering in Messenger Plus!? And if so, do you filter on the word "says"? If so, than there is your problem; Filtering on the word "says" can cause such problems ...
(filtering on "says" is never a good thing and not recommended at all)
see "CookieRevised's reply to Custom Emotion Sounds & Word Filters"
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other than this, and other than the things said in this thread (make sure nothing is blocking the servers) I have no idea (yet)...