mplayerplug-in won't emerge for firefox-bin 2 depends on firefox 1.5. I'm not sure if it is compatible with ff2, so this may be upstream...
*** This bug has been marked as a duplicate of 107579 ***
I don't think this bug is a duplicate of bug #107579. At least not in the sense that the solution of bug #107579 is appliable here. Bug #107579 says you should set mplayerplug-ins USE flag gecko-sdk to not need mozilla, i.e., use mozilla-firefox-bin. There is no gecko-sdk anymore in mplayerplug-in! How can one get mplayerplug-in working with moziall-firefox-bin 2?
mplayerplug-in won't emerge against anything -bin, missing the needed headers and other stuff. Can't do that, period. You need mozilla-firefox or seamonkey (NOT -bin).