"Save-as" shortcut not working for anything
Follow this guide, you'll be able to track down a few more places that may be interfering.


System Preferences -> Keyboard -> Shortcuts


This is the obvious one that you'd think of. However, you said you've checked and can't find anything, so we'll move on

System Preferences -> Dictation and Speech -> Text to Speech


It's unlikely, but possible that you bound "Speak selected text when the key is pressed" to something else (as I have.)

~/Library/Preferences/com.apple.symbolichotkeys.plist


If you can't find anything else take a look here and see if you spot anything that's using the keys you want unbound.