Similar things also happen with other short cuts sometimes such as the "V" key. It's really annoying and is slowing me down so If anyone can shed some light on why this happens I'd be very grateful.
NB. I'm using PS CC.
If you press Alt or Option key the menu bar shortcut key are toggled and become active pressing E will open the Edit menu, F file menu, I image menu, L layer menu, Y type menu, S select menu, T filter menu, V view W window menu and H help menu.