Hi , I've just confirmed that I have the latest version of Messenger as per your 'post'.
My cousin and I frequently conduct video links via Messenger, for the most part without problems. (This while both on W7)
On the 25th Oct I installed W8 and since then we have had intermittent problems where the sound goes after a few minutes of the link being made. Perhaps a W7 to W8 mis-match we thought. However, this morning my cousin successfully upgraded to W8 but just this evening we found the same problem occurred perhaps even worse than before.
We have both checked our Logitech drivers are the latest and all vision and sound settings. Device Manager states all hardware etc ok. Can you possibly suggest anything further for us to check please?