Yo,
when I want to change the weapon with my mouse wheel, it seems quiet random when it will actually change the weapon.
Scrolling one, two or three till the weapon is finally changed...
I'm using a Logitech G5 with Logitechs drivers (software) installed on Windows XP 64 bit.
I remember having this in some other game some longer time ago (dunno if that even was on this OS now, but definitely before using that mouse) but don't remember in which game.
Anyone else?
Any solutions?
btw,
I could not map my 4th mouse button as well.

Have the same issue with Logitech Revolution VX...but got used to it ,)

I have that problem with my Logitech mx510 as well.

This is mainly a guess and possibly selective remembering but I didn't have this problem with a standard dell mouse that had no extra mouse drivers just what windows used. I did have it with my new razer krait mouse that requires its own drivers to run.
If you have a bog standard mouse about you could try using that and unistalling your logitech drivers to see if that sorts the problem out.

There's no need to change your drivers, just go into the game's control settings and turn up the mouse wheel sensitivity.
As for mapping the button, I don't have any ideas.

Such simple thing...works, THANKS!! :)

mouse wheel sensitivity??
There's actually something like that?
rofl

I was as surprised as you when I saw it. This is the only game I have ever seen it in. Usually you will find a mouse movement sensitivity setting, but a mouse wheel sensitivity setting... it just seems unnecessary. Obviously they did something to make it necessary, since it does fix the weapon switching issue.
I had a thought on your mouse button issue; since you definitely can't configure the mouse extra buttons within the game (my MX510 has the same issue), why not use the Logitech SetPoint software to set that button to a particular keystroke that matches the keyboard function in the game?

Yeah, I had the same problem. Solved it with the mouse wheel sensitivity option. Don't know why it's there though, maybe there all folks who likes to scrooooll before reaching the next weapon. :P

Well, a few mice have wheels that don't click, they just smoothly roll around, so there isn't like a click to tell the person when they hit the next setting or whatever, so they can mess around with that setting until they like however much they have to roll until the weapon switches.