Dear All,
Just to let you know, I had face numerous freezes after updating to Adobe Air 3.90 with signage player on the mediaplayer 300. Sometimes signage controller manages to recover, but once in a while it just stops.
I had tried everything from updating/downgrading the signageplayer,re-encoding video clips, clearing cache and unregistering. And the only thing that works is downgrading the AIR version.
Here's the official link from Adobe if you want to go back. Wasn't allowed to post the external link but you can search for it.
So far, I'm using 3.4 as it's seems to work on my other players without problems.
Just sharing so if you face the problem you can try this option.