I am not sure about the extent of this problem but after thirty minutes of research I finally solved a long standing flaw with the SetPoint driver and the Source Engine (possibly affected other games as well, but for me I only ever had problems with the Source engine.)

While playing any Source engine game with my Logitech G5 mouse and SetPoint 4.72, mouse5 would reduce my DPI setting, instead of being a usable button. The only fix would be to ALT-TAB out of the game, use the proper DPI buttons on the mouse to reset the DPI and ALT-TAB back into the game. If I were to hit mouse5 again, I would have to rinse and repeat the above solution.

This to say the least, has been very annoying because I am able to use mouse5 properly in other games and I occasionally have the subconscious urge to press it while playing a Source game, causing the ALT-TAB fiasco.

I found a post on the Logitech forums by "rlowens" with the fix. It is dated for 2007, which I found somewhat shocking that Logitech simply didn't fix it themselves during the past two years. The problem originated with SetPoint 3.1, and the version I currently use is 4.72.

But enough of the back story, let us move onto the fix.

This fix requires you to edit the two following files:

• C:\Documents and Settings\All Users\Application Data\Logitech\SetPoint\Devices\PointingDevice\1000077\1000077.xml
  
  
• %userprofile%\Application Data\Logitech\SetPoint\user.xml

The Logitech forum post suggests that you simply delete user.xml. If you have several profiles for your applications and games, deleting this file will cause you to rebuild all your profiles. Instead I will tell you how to repair the file.

Editing 1000077.xml changes the default profile so that when you decide to make another profile for another application, the fix will be part of the new profile.

Before you begin, make sure SetPoint is closed. Open your Task Manager (CTRL-ALT-DELETE, or right-click your Taskbar) and verify that there is no SetPoint.exe

Now open 1000077.xml and change:

GameModeButtonResDown="5"
GameModeButtonResUp="6"

to

GameModeButtonResDown="9"
GameModeButtonResUp="10"

Save and close the file.

Next open up your user.xml file, and apply the same change to every occurrence of GameModeButtonResDown and GameModeButtonResUp similar to how you did it for 1000077.xml

I should also point out that this is a fix for Windows XP 32-bit, and obviously if you don't have any problems with any of your mouse buttons, you should not bother with this fix. If you do not feel comforitable making these changes I suggest you back up the two files before hand.

I am including both the original link as reference and also the original post should it no longer exist in the future.

Reference: http://forums.logitech.com/logitech/board/message?board.id=software_mice&message.id=4481#M4481

Quote from rlowens

I think I found the source of this particular problem.

In the device source files for the G5 original, the buttons were internally numbered:
1: Left
2: Right
3: Middle
4: Thumb (back)
5: Minus
6: Plus
7: Tilt Left
8: Tilt Right

And in the top of the device defaults file (C:\Documents and Settings\All Users\Application Data\Logitech\SetPoint\Devices\PointingDevice\1000053\1000053.xml in SetPoint 3.30 on my XP machine), there are these entries:
GameModeButtonResDown="5" GameModeButtonResUp="6"

In the device source files for the G5 mk 2, the buttons are internally numbered:
1: Left
2: Right
3: Middle
4: Thumb Back
5: Thumb Forward
6: (none)
7: Tilt Left
8: Tilt Right
9: Minus
10: Plus

But, the device defaults file (C:\Documents and Settings\All Users\Application Data\Logitech\SetPoint\Devices\PointingDevice\1000077\1000077.xml) still has the same settings:
GameModeButtonResDown="5" GameModeButtonResUp="6"

Someone with a G5 mk 2 mouse try this:
1. Close SetPoint from the System Tray

2. Edit C:\Documents and Settings\All Users\Application Data\Logitech\SetPoint\Devices\PointingDevice\1000077\1000077.xml and change
GameModeButtonResDown="5" GameModeButtonResUp="6"

to

GameModeButtonResDown="9" GameModeButtonResUp="10"

3. Delete or rename your user.xml settings file to reset the mouse settings to the new defaults (delete %userprofile%\Application Data\Logitech\SetPoint\user.xml )

4. Re-launch SetPoint.exe and try it out.

As soon as someone confirms that this helps, I'll make these changes in uberOptions so you just have to install uberOptions to fix this. I'm not sure what (if any) problems this will correct.