Favicon trouble !!!

Do favicons differ in browsers?? I didn't think so ...Until I saw the difference myself!

Those were the favicon in my ie8beta2... yahoomail luks totally out of the way doesn't it?and so does gmail! and look @ orkut - picassa ???!!!!
Look how the same sites' favicons look just the same as the old ones in FF 3.0.1 .. Beats me !!Does anybody know why these favicons have these uncanny shapes?? Do tell me !
Btw, if anybody noticed my gmail favicon in FF.. the cute blue one.. Its a userscript that i installed from THIS place.If you simply want your Gmail FavIcon to change in a pretty fashion,install it.. works with FF and opera.It has three icon-states by default:

* No New Mail: Red envelope. ScreenShot: No New Mail

* New Mail: Blue envelope. ScreenShot: New Mail

* Unread Chat Message: Orange envelope. This icon changes back to your mail status every two seconds. ScreenShot: New Chat Message

Any takes on why the favicon's changing enigmatically.. pls write tat in my comment page!waiting for replies!

UPDATION: (8 oct,2008)

Get a load of my taskmanager...Same Prob... wat now? OS probs?? :P
P.S: I'm loving it (the exceptions) !