Problems assigning F7-F8 to Hotkeys.

[Starionx]

This has baffled me for days, and I've tried all sorts of things to fix it, but can't.

What I want to do - Assign F7 to 'Multimedia: Previous', F8 to 'Multimedia: Next' (Global keys) in the Hotkey preferences screen.
What actually happens - When I press the F7 key, it shows 'Ctrl+Tab'. F8 shows 'Ctrl+Shift+Tab'

If I save these settings and press the F7/F8 keys it does behave correctly (the previous/next song plays). However, if I now press Ctrl+Tab/Ctrl+Shift+Tab, those key combinations also skip to the previous/next songs.
I've tried different keyboards and they all do the same thing. I used a program called SharpKeys (which reassigns keys) to see what it thinks, but it doesn't see the keys as F7/F8. Something weird there... However... I have an Autohotkey script that displays keystrokes on screen and when I press F7/F8 it shows F7/F8. I have a number of other scripts that use F7/F8, and they all behave normally. If I go to my Logitech Mouse software and try to assign those keys to the mouse, they also show F7/F8. Games that use those keys also behave normally.

I installed MusicBee on my laptop, and in the Hotkey preferences, when I pressed F7/F8, it showed F7/F8. That's when I started banging my head against the wall.  
I then went to the MusicbeeSettings.ini on the laptop and compared them to the file on the PC and found that the Multimedia: Previous/Multimedia: Next settings had different key codes. I copied the codes from the laptop to the PC. Restarted MusicBee... and now F7/F8 don't register................. *RAGE*
The good news is I can now scroll through tabs in firefox without skipping songs.  

I'm stumped. Has anyone got any suggestions?

PS - I'm using Windows 7 (64bit) on both Laptop and PC.

Edit - One thing I forget to mention. These keys are also used by the keyboard as Media keys, but only when used with the Function key.

[psychoadept]

I suspect this is because the Multimedia Hotkeys are designed specifically to work with the computer's multimedia keys.  I don't know all the mechanics of that, but assigning F7/F8 to Playback: Previous Track and Playback: Next Track and marking them as global should have the result you want.