Well, it seems I’m not the only one with this problem and I came across a website that offers a solution: http://www.ben.pope.name/logitech.html.
The solution consists of two simple registry files that will exchange the “normal” F-Keys and the enhanced F-Keys. This means, when F-Lock is deactivated, the normal F-Keys are in place. When F-Lock is activated, the enhanced commands are set. Nice idea!
Since the iTouch Software will no longer work with this configuration, you should disable its automatic launch during startup. Simply download X-Setup Pro from http://www.x-setup.net/, install it, launch the “Classic” user interface and move to this path:
Startup/Shutdown\Startup\Windows\50) AutoRun - Part 1\AutoRun Programs (All Users)
The item you need to disable is called “zBrowser Launcher”. Simply hit “Show Info” to verify that this really launches the Logitech configuration. Hit “Apply” and restart your computer. Done.