Flash videos do not work properly on my Mac. On this Vimeo video, for example, it shows only the beginning frame, and audio stutters like crazy, playing audio for a quarter second or so, then silence, then playing again, etc.
I have Flash version 10,0,42,34 on Mac OS 10.5.8. It's a PowerBook G4 (PPC). I tried it in Firefox 3.5.5 and Safari 4.0.3.
I tried reinstalling Flash, restarting the computer, and using a fresh user profile in Firefox (so that no extensions are interfering with the site), loading the video fully before playing, but nothing helps.
I noticed that youtube videos work better, once loaded enough, although the picture does halt briefly once every 10 or so seconds, even when it's fully loaded.