So, it took me ages and I started living with this Bug, that I just couldn’t play any flash videos through Firefox on neither my Windows XP nor Vista machines (slightly embarrassing for a flash developer). Googling the problem a couple of months ago, all results seemed slightly unsatisfactory. I re-googled, and now did find prper solutions. OK, the web might now offer them, although I thought one more Post about this won’t harm. The best solution that did work instantly for me, is the one Mozilla offers on there site.

The main issue seems to be, that when updating to a new version (which I tried about 10 times), the old version actually does not really get deleted. Removing the flash-Player through the control panel is just a waste of time, but Adobe does offer an uninstaller, that works just fine.

Follow the instructions found on the above link, this has finally resolved the issue for me, and I don’t need to open IE just for flash videos any more.

here a copy of the instruction from
Flash video (including YouTube) freezes in firefox

First try installing the latest version of Flash using this procedure to see if that helps:

1. Download this uninstaller from Adobe.com
2. Download this installer from Adobe.com
3. Close Firefox
4. Run the uninstaller, then the installer
5. Open Firefox

tha worked for me. Amen