I'm glad to see the original problem (more or less) solved with a replacement keyboard.
I've been using this keyboard for about a week, and I really like the possibilities it offers. I have, however, run into a similar issue that I have found NO resolution for either with several web searches NOR with a search here. Actually, the one web search that turned up anything pointed to this thread.
The issue is, occasionally when I start up my Win XP Home homebrew PC, I get a message once at the desktop that "LGDCore.exe failed to initialize properly" and I have to press "OK" to terminate it. My LCD screen works fine even after that, but it is the "G" keys that are inoperable at that point. I have a few applications (iTunes, BF2, TeamSpeak, Calculator, etc.) mapped to the G keys in the default profile, and after that particular error message comes up, none of the G keys work.
What's more strange to me is that I can restart and get the error message several times in a row, and then one time it will start up normally and everything is fine.
Strange. Logitech's site has NO helpful info on this issue. This first software iteration is crap...I hope they're working on an updated version.