brightness, media, and volume keys broken

I am at my wit's end trying to restore functionality to my special keys on my late 2007 macbook running OS X 10.6.8.

Some time two days ago something happened and now suddenly I cannot use the mute key (F10), the volume keys (F11, F12), the brightness keys (F1, F2), or the media keys (play/pause (F8), forward (F9), rewind(F7)). Probably the media eject key is non-functional too, but I'm afraid to put in a CD and test it in case I can't get it out.

Interestingly, the exposé "all windows" button (F3) works fine, as does the dashboard button (F4).

I think I instigated the problem installing and poorly uninstalling logitech command center or maybe somehow poorly uninstalling logmein.com sound drivers, but that's just guilt by association AND I've tried everything I can think of in terms of uninstalling those apps, reinstalling them, and carefully uninstalling them correctly. Still, my half-baked best theory of what happened is that the logitech software reassigned some key functions somehow.

I am using a logitech K750 external keyboard and a M510 mouse via a unifying receiver. The keyboard is the version intended for a PC but was working pretty fine on my macbook (windows key worked as command key, Fn+volume keys worked as expected). I installed Logitech Control Center (LCC) for Macintosh because I wanted to adjust the horizontal scrolling via the mouse wheel (it was way too fast for my tastes). Installation of LCC prompted the keyboard setup assistant ("Your keyboard cannot be identified..."), even though I was only interested in adjusting the mouse and the keyboard was working fine. I ran through the setup assistant as instructed. Roughly since then, I've lost volume adjusting functionality on both the external (logitech) and built-in keyboard as well as all the other functions mentioned on the built-in keyboard.

I've been obsessed with this the last day and a half with no luck. Here is a pretty comprehensive list of what I've tried to fix the problem, though I may forget something since I've done so much:

-removed all peripheral hardware.

-use a different user account.

-SMC Reset

-PRAM reset

-Safe mode

-System preferences reset/ inspect all settings related to keyboard, universal access, text to speech according to the numerous help files I found online. (yes, I unchecked "Use all F1, F2, etc. keys as standard function keys"

-turned off all google chrome background apps and inspected the key bindings of all chrome extensions.

-Removed Cache folder from library folder.

-removed recently installed software that I suspected might be related, reinstalled, re-uninstalled.

-installed OnyX and run all the maintenance/restoration routines I saw in it that didn't sound too scary.

-Turned on keyboard viewer and verified that each guilty key is recognized by the system when I press it (they all are!).

No luck. I don't have a snow leopard install disk but I just bid on one on ebay because I'm starting to feel like my only option is a time-machine full system restore 😟

Please help! I'm still holding out hope that there is some simple way to get under the hood and re-assign or reset the keys. I can't even figure out how to disconnect the logitech peripherals (keyboard and mouse), though I've removed all the logitech software I can find.