I have a Logitech K350 keyboard and an anywhere MX mouse which use their unifying usb receiver plugged into a MacBook Pro running Snow Leopard. I have Logitech Control Center 3.10 installed. The keyboard and mouse work, but the control center sys preference app doesn't see the keyboard. The unifying app does see it, but with out the pref app seeing it, I can't config the keyboard.
Edit: turns out it's a known bug.
I just got off the phone with Logitech tech support. It turns out their System Preferences app is not seeing a lot of their keyboards... it is a known bug with v3.10 of the app. Look for an updated version starting next week for an update.