If your mouse buttons aren't working as programmed, the issue is most likely with the configuration. You can check your mouse button settings and change them in the Logitech SetPoint Mouse and Keyboard software.
To change the function of a mouse button:
Launch the Logitech SetPoint Mouse and Keyboard Software.
Start > Programs > Logitech > Mouse and Keyboard > Mouse and Keyboard Settings
Click the My Mouse tab at the top of the SetPoint Settings window.
NOTE: If you have more than one Logitech mouse and the LX5 Cordless Laser Mouse isn't currently displayed, click the down-arrow icon next to the current product name and select it from the drop-down menu that displays.
Choose the mouse button you want to customize in the Select Button field.
NOTE: If the Button Settings screen is not currently showing, click the mouse icon on the left toolbar to display it.
Choose the task you want to assign in the Select Task field.
NOTE: You can click the "?" icon next to Button Settings for detailed descriptions of these tasks.
Click Apply to save your settings and then OK to exit SetPoint.