Simply place the two new files "NPSWF32.dll" and "flashplayer.xpt" inside your Mozilla Firefox Flash plugin folder or if you have old ones in there already then replace them with the new ones.
note: you have to have Mozilla Firefox Flash Plugin v1.3 by Sherpya installed
link to the files:
Flash.zip - 2.64MB
I take no credit for the plugin, I'm merely providing newer files so that the content that requires the newer flash plugin can now be viewed.
Also, it looks like Firefox 2 is getting old, I know there's been a mention of how Firefox 3 is unstable with BartPE but here's to hoping that someone makes it work.