Start by rebooting your system. Perhaps you have simply initiated soem weird input mechanism by holding a key too long or pressing an unusual key combo inadvertently. Likewise, check accessibility options in your system settings, input utilities, tablet writing tools and of course anything that can "steal" inputs like live messengers. as for AE - reset the character palette and also delve into the associated flyout menu and the preferences. Enabling alternate inputs liek RTL writing or having chosen a language that isn't supported by our input scheme and has no suitable fonts on the system can have all sorts of weird effects. Whatever it actually is - I hope those clues cover all bases and should get you on track.