Hrmmm... A hotkey cannot be set to more than one key, so it's weird that it would be doing that. They're also not menu specific - meaning that the hotkey should be the same throughout all of the menus.
I'm not familiar with Maya on Mac, but I'm sure it can't be that different.
Have you tried just hitting the spacebar and switching between windows that way?
Professor of Digital Arts
Digital Media Arts College
Boca Raton, Florida