Like already said in the previous post, the flashplayer nowadays is a real resource hog. Unfortunately, I ran into quite some problems in using the afore mentioned alternative Linterna Magica. Luckily there are more alternatives around, and one of them is Viewtube. Also a userscript that basically does the same as Linterna magica, but aparently with a lot less hassle.
Flashplayer alternatives revisited25 04 2013