I've had this problem occur on two PCs so I thought I would post the fix (courtesy of Brian Keller) since I'm likely not the only person running into this.
- Go to this page to install Flash (uncheck Google Toolbar, no idea what that has to do with Flash)
- You'll get a confirmation screen that will say it's successfully installed, but you still won't be able to watch videos on MSN, YouTube, etc
- To fix, Run C:\Windows\System32\Macromed\Flash\FlashUtilXX.exe where XX is the largest value you find in this directory. (For me it’s 9d, but it used to be 9b)
- You'll be prompted to close all browsers and you're done
* Updated Jan 11th for Windows 7/Internet Explorer 8 64-bit - Go to the directory C:\windows\syswow64\Macromed\Flash\ to find the FlashUtilXX program.