Jean........the paint on your shutters is chalking. This could be caused by a few things:
1. Very low quality paint
2. Interior Paint used outdoors.
3. Oil based paint.
4. A dark color tinted in the improper base - the colorant load is too much for the paint.
Power wash the shutters - ensure all the chalk is gone. Prime with an exterior oil primer (is sticks better to residual chalk than latex) - then two coats of 100% Acrylic latex exterior paint.
Buy the best you can. Glidden Evermore, ICI Dulux, ICI Fortis are all very good exterior paints.