Ok, just had a chance to try out the advise given by dronecatcher and redheeler. In a word, '
great'! So many thanks for the feedback.
This is coming to you from the same core duo MBP1,1, and have been watching 720p Ytube videos using TFFox with no problems.
For info, the following was what I was seeing prior to enabling MSE. Wondered why after right clicking on a video page there were no references to Quicktime below the 'Inspect Element' heading, as shown in dronecatcher's 2nd screenshot.
Same after enabling MSE.
The following screenshot indicates YouTube running flawlessly in fullscreen 720p.
For YTube playback, I've only noticed 2 minor disadvantages with this TFF version compared to FF 48.02.
i) Beachballing for approx 3-4secs after selecting a chosen video.
ii) After shutting down the computer, an hour later in TFF and selecting a YTube video, it wouldn't play. Met with the same problem message as seen in the 1st screenshot above. Second attempt still wouldn't play. Noticed that MSE option was no longer active in TFF preferences. Re-enabled MSE and correct video playback was resumed.
In summary, a very pleasant experience using TFF under Snow-Leopard.
