Hi, I'm having this exact same problem with my Logitech G510. I'm running Windows 7 x64. I just installed the newest version of Logitech Gaming Software (8.56.109) from scratch, and the included Logitech LCD applets do work. I'm running the newest version of AIDA64 Extreme. If there's any more info I can give you to help diagnose the problem please let me know.
Cheers.