I'll start off by saying I've not had this problem in previous installs of Windows (though usually XP), and I've owned this mouse for 2 years.
I formatted my computer earlier today (Win XP 32-bit) and installed Windows 7 Professional 64-bit (to take adv. of the 8gb I have; XP 32-bit only recognises 3gb).
However, I've noticed that since doing so, I've lost the functionality of my middle-mouse button. I can still scroll on websites; scrolling works fine, but clicking it doesn't work - And this is a problem as clicking middle-mouse is my TeamSpeak/Ventrilo push-to-talk key; a button I use quite a lot.
I also used to find it faster to us the 'auto-scroll' feature where you click the middle-mouse button on a long website, and can push the mouse back and forth to automatically scroll at high speeds.
I thought that perhaps it was just an incompatibility with Win 7 in general, but friends also on Win 7 (though they have different mice) tell me they don't have this problem.
I went into a game (Battlefield 2) to see if I could map a control to the middle mouse button (which by memory is 'MOUSE 3'); basically to see if the issue was just with Windows in general, or whether the entire functionality of the button itself was not being recognised. Anyway, pressing the middle mouse button to map a control did nothing, as though I may as well have been tapping my desk.
I went and did something I've never had to do for this mouse, and downloaded the 'Setpoint' drivers from the Logitech website and installed them, and restarted my PC after having done so.
However, in the config of setpoint, everything seems to be configured correctly; it just still doesn't work.
Despite installing these drivers, I still have the same issues as described above.
On a lesser note, the G5 has two side-buttons; in XP these served as 'forward' and 'back' in web-browsers, but only to 'back' button works, the forward is functioning (or rather not functioning) just like my current middle-mouse click. It might be interesting to note that when I tried to map a BF2 key using the 'back' button, it said the bind was 'MOUSE 3' (which should
be middle-mouse, whereas it itself should be 'MOUSE 5', and the 'foward' button 'MOUSE 4'.
Despite the bind calling itself 'MOUSE 3', the 'back' mouse button does not act with the functionality that my middle-mouse click should have.
I appreciate this isn't a typical question and you may not be able to help; if not I'll just adapt to not using the middle-mouse click, but any help you can offer would be great.