Well, when you first siad that the shortcut key wasn't working, my instant thought was "Make sure that Cpas lock isn't on" but when you said all other shortcuts were working, i knew it was something else...
When you got go to file>> Save as, right next to it should be a sequence of letters (the shortcut) this one should say Ctrl+S. If it doesn't say this then you'll probably find the shortcut has been disabled for this command.
So to fix this go to: Window>> Settings/Prefs>> Hotkey editor.
Now in this window on the right hand side you should see a small area called "Assign new Hotkey" in this area type 'S' in the key menu, and check the 'Ctrl' option.... then click 'Query' if this Hotkey command is still active for save as it will tell you...
"Ctrl+S is asigned to 'Save scene from file'"
If it is no longer assigned to save as then we know what the problem is.... to fix this simply use the Catagories menu on the left hand side of the Hotkey editor, and select file... then in the commands menu select save scene as.
Well if this is not the problem, i'm sure someone else will post with another solution, and watch it be a really simple one :headbang:
Well lets us know if this doesn't help.
"Your weapons are no match for ours! People of Mars, surrender!"
"Um, this isn't Mars. This is Earth."
"Earth? Earth-with-nuclear-weapons Earth?"
[long pause] "Friend!!"