Itunes' iphone retore button disabled

[yusiye]

I upgraded my iphone4 to ios5. Now itunes' iphone restore button is disabled for some reason. How to enable it? I want downgrade to 4.3.3

what can I do to enable the restore button?
Thanks

 

[yusiye]

Finally i got it to downgrade, but somehow i'm stuck in the recovery mode. i tried recboot and tinyumbrella. but none works. this is going to be a long day for me. ahhhhh