Hi Stefan,
Uh, using x2goclient with "lan/no image compression" isn't the same as running ssh -X and forwarding the display. While your results surely
I see what you mean now..
However, I have now spotted that the issue goes away completely if I set my x2go session to use only 256k jpeg compression.
That also seems to make remote video like youtube usable.
I think, based on that, that running my X session entirely over SSH becomes redundant - it must have something to do with the x2go compression.
Of course, the main cause of the problem is still Firefox, but for the purposes of dealing with misbehaving applications like this, jpeg seems better.
It's possible there's something wrong with the Debian packages though, because many compression methods like Tight, RDP etc simply crash the session immediately before it's shown.
Thanks, Carl