Help with Clear Overcoat!!!

Pigment (or in the case of a clear flat coat, a "matting"  agent) settles at the bottom of the can "on the shelf".  20-30 seconds isn't really enough to mix the paint thoroughly, so your coats may have had a higher than normal concentration of the matting agent, which may cause the white haze.

What's the air temperature and humidity like at your location? If it's relatively cool and humid, when the paint is applied, as the solvent and propellant evaporate, it may cool the surface enough to cause condensation, which can also cause a whitish haze (the effect is known as "blooming")

It sounds as if you may have sprayed too much/too heavily and/or didn't shake the can sufficiently before starting. (You should shake the can for at least 3 mins, preferably longer)

Applying a clear lacquer coat over enamel usually isn't a problem provided that the enamel coats are well cured - at least 24 hours, preferably 72. If it was under 24 hours, it may have been caused by "outgassing" of solvents from the enamel layers.

If the ambient temperature was low, it could also have been caused by condensation of water on the surface of the drying paint.  

If the haze is not too heavy and the layers of paint/lacquer not too thick, you might (no guarantees here) be able to kill the haze by applying a coat of clear gloss, then re-apply a very light coat of the flat clear and see how you go from there. If this does not work, the other alternative is to strip the paint back and repaint.