Unfortunately I am unable to provide you a link, however it has been reported here and other forums that the Malaysian Civil Aviation General confirmed during a press conference that no ACARS message linking to malfunctions of the aircraft were sent to Malaysia Airlines Operations Centre.
It is unclear whether the ACARS downlink transmission suddenly stopped, as I am led to conclude based on this report, or not. MA and Malaysia authorities are being pretty tight lipped so far.
To all those people placing high hopes on ACARS, you probably don't know what it is..
It is only the datalink itself, just the system delivering a message, it doesn't make the message.
Messages can be directed (amongst others) at ATC, the airlines operations control or the technical department and it can be used to access external providers, for instance to get wx reports.
It can be uplinked or downlinked an can be automatically or manually.
Now the messages from AF447 originated from the ACMS (look it up) that reacted on several active faults that it sensed. ACMS downlinked those faults automatically to AF's tech department as it is apparently programmed to do.
That works in my airline the same but these are usually customer options, so who knows how Malaysian has set that up or what system they have in place.
Anyway you cannot conclude anything from the absence of downlink reports.
And for the conspiracy theorists suspecting MAS to keep messages for themselves, in my company it is not allowed to sent any sensitive information (like Creditcard numbers of customers) because it is easily intercepted (Get your free ACARS decoder on the 'net).
Would be something if it turns out afterwards that MAS had withheld information.
Don't think so!