Blank screen on streaming/video sites.

Hi. I'm having the same problem that a few people seem to be reporting with streaming and video sites. Some sites such as youtube will work fine, but streams on justin.tv (for example) will just show up as blank, not even as loading.

I have tried all the fixes on this page:

http://helpx.adobe.com/flash-player/kb/flash-player-games-video-or.html

and have tried checking "allow third party flash content to be stored on your computer" on this page http://www.macromedia.com/support/documentation/en/flashplayer/help/settings_manager03.html. I could not even check the box. Deleting the cache folders did not work as a fix to this. Also when I tried disablling hardware acceleration on the settings panel the settings would not save.

I am running a new install of Windows 7 (64-bit) on a new PC; I haven't been able to use any streaming sites since I first started using it. It is not specific to one browser, all have up to date versions of flash and I have tried Chrome, IE and Firefox - none work. Can anyone help?