Intellimouse and CS

I just got an Intellimouse Explorer (the silver one) and got it set up and working. Very nice mouse. The only problem is in Counterstrike I have the thumb button bound to "+duck", which binds ok but when I press the button it's like a really quick click rather than a click and hold. I tried switching the button assignments, when I did the button I assigned "back (default)" to did the same weird thing and the thumb button worked normally. This makes me think it's something with the Intellimouse software rather than the mouse itself. Whatever I bind "back (default)" to does this quick click thing rather than a click and old as you'd want it to... The problem is in Win98, in Win2k it works prefectly. Any ideas? (I know, assign the button to some keyboard key and bind +duck to that... I'll do that as a last resort)

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