Just recently, and I cannot quite be certain when, video on some websites I use stopped playing in Safari and Firefox on my Mac instead being replaced by a QuickTime logo with a question mark. There are plenty of folk experiencing the same issue but no real answer. The most suggested fix is to repair permissions but this is not what my issue was.

I finally found that the video streams in question are Windows Media Video streams. QuickTime does not play the format and so gives the question mark.

To fix this issue I just installed the free version of the Flip4Mac WMV Player which installs the appropriate codecs/plugin for QuickTime X.

Now I can get on with watching the NASA Ares launch.