If you've been experiencing choppy audio when viewing YouTube videos, the problem is with the current release of the Adobe Flash player (11.3). Apparently the problem is ugliest on XP, but it affects all versions of Windows and Mac OSX, and all browsers, including IE, FF and Chrome.
The solution is to close any open browsers, uninstall the plugin via the Add/Remove Programs applet, and then install Flash version 10, which you can download
here.