Oh joy, sounds just like an old car of mine.... 4 ways would work, but the signals wouldn't turn on when I clicked the switch, I even replaced the unit and it wouldn't work.... (Know the unit was good).
nofronts, sounds like you have an electrical problem. Now reason I say that is if all fuses check out, and you replace the switch unit, and they still won't work, then you might have to take it to the stealership, and have them check it out. I paid the stealership for 2 hours to track down my electrical problem in my old ride, and they told me they couldn't figure it out.... how nice...