You're not alone. I have the same kind of Mac and whereas YouTube etc used to play perfectly, since first installing Flash 10 I now get exactly the same problems as you. I too have done pretty well all the things you have tried, including ditching Flash 10 and going back to 9, but it's no good. I thought it might be something to do with Safari 4, but I get the same problems in Firefox.
I don't know what's in Flash 10, but I don't like it. I suppose it's some kind of preferences clash.
Thanks for your post. I'm wondering what the CPU power is on your computer. My computer is a used one and only has 550 MHz. Someone told me that this is probably the reason for my difficulty in playing Flash video: my processor simply isn't fast enough. If I use the Mac "Activity Monitor" to look at CPU usage, my CPU power is indeed totally maxed out by trying to play Flash videos.
If your computer has the same CPU speed as mine, and once upon a time you were able to watch Flash videos OK, that means that the CPU speed is actually NOT to blame, not on your computer or on mine. But if your CPU is a lot faster than mine, then maybe it really is true that my computer is just too slow to watch videos on the web.
My youtube videos have the same problem. The only way to see such a thing properly is to begin everytime after a break from the start; then you see the video just to the point of the last break without a pause (and just a bizzy little teeny mini more!!!) and then after the following break return to the start. So you need for a playing time of 2 minutes 56 secs a real time of half an hour until you can look the whole video properly running without any breakings. It' s a pitty. And all that since the new version of flash is on my computer! I don't want to blame your new flash player version (we in Germany say, that a horse given as a present must not be critizised by judging the teeth in the mouth of the animal), but it seems to me - a bloody analphabet in computers, but a friend of good entertainment - that this product is not ripe enough to be in the public. Your flash player has made me a lot of joy : hearing the bbc, looking the youtube videos and all that, - but now it is all gone with version 10 and the plugs....
My processor is 1.07GHz, so about twice as powerful/fast as yours, but I have just the same problems as you, and like you I had no problems before. Yes, I'm sure the processor is to blame in some part - they want us to buy new computers with Intel processors inside - but what bugs me is that we can't go back to the old system which worked perfectly. I also have a good broadband connection - over 5MB/sec, and still it cranks on. Having said that, Safari 4 does make some pages easier to load.
I wonder if anyone from Apple or Adobe ever reads these pages?
Sorry, I wasn't clear. My computer NEVER played flash videos properly, with any version of Flash. Considering that Flash is maxxing out my CPU power (as measured by the Activity Meter) I suppose that slow CPU speed really IS the cause of my problem. Since you have a faster computer, and your computer used to play the videos OK, it seems likely that your problem is SOME OTHER mysterious problem.
You might be pleased to know that in English we have the same expression as the German which you quoted
"we in Germany say, that a horse given as a present must not be critizised by judging the teeth in the mouth of the animal"
In English, we say "don't look a gift horse in the mouth."
You could be right, but don't forget my computer played things fine until I installed Flash 10.
What's more, you might like to check out this page, which will show you that even the fastest computers are suffering: