My problem is this: I recently tried to install Windows 7 64bit on a computer. Everything went ok, drivers, software but when I tried to play a video on Youtube, after a few seconds it changed the quality to HD, grayed out all other selections from quality and displayed " An error has occured, please try again later" After a refresh, same thing. I tried older version of Flash, the same thing happens. The problem is the same on Internet Explorer. I tried reinstalling the OS, only installed network driver, went to youtube and installed Flash Player for IE, the same thing happened. After this i tried it on Firefox, it said that it doesn't have flash player installed but it played ok, without problems. After installing Flash the same problem occured. Please help me because I really don't know what else can I try. Thanks!
Usually HD playback problems are related to Hardware Acceleration, which is your DISPLAY drivers, more than the network drivers. In some cases, disabling acceleration resolves the problem, in others ENABLING it resolves it, but I'd recommend updating your video drivers from the manufacturer site (not Windows - see:http://forums.adobe.com/thread/945765) and then try the HD again, toggling Hardware Acceleration on and off to see which works best.
If that doesn't change anything, try the "debug version". www.adobe.com/support/flashplayer/downloads.html