Ok, so Microsoft slipped a Firefox extension in with some updates recently. Chances are you all have it if you run FF. Go to Tools -> AddOns and look for Microsoft .NET Framework Assistant. There? Yeap, thought so. Irritating. Among other things, it actually alters your browser identification string. Go Microsoft!

Of course, you can't remove it via the addons panel, you have to do it via the registry and deleting files off the hard drive. Go Microsoft! Here's some quick instructions, gotten via http://nambulous.wordpress.com/2008/08/ ... m-firefox/.

Launch the registry editor via start | run | regedit
go to HKEY_LOCAL_MACHINE/SOFTWARE/Mozilla/Firefox/Extensions
delete the value on the right, or just delete the whole extensions key if you want.

go to HKEY_LOCAL_MACHINE/SOFTWARE/MozillePlugins
delete the key @microsoft.com/WPF,version=3.5

on the hard drive, go to C:\Windows\Microsoft.NET\Framework\v3.5\Windows Presentation Foundation
Delete everything in this folder

In Firefox, type about:config in the address bar and click ok on the warning.
In filter type microsoft.
find "general.useragent.extra.microsoftdotnet" and "microsoft.CLR.clickonce.autolaunch", right click on them and choose reset, then close and reopen Firefox

That should do it. The values should be gone from about:config and the add-on will be gone from the addons. Good times to be had by all!