Variable visability, hidden units question

[Montana Grizz]

I've noticed that when I highlight my opponents visable units that some that use to be visable under pre-1.03 are not highlighted.

However, when I cycle through the fire phase sometimes a unit of mine will say that it can fire, but I can't see a highlighted unit to fire at.

If I scroll my cursor around it will show an enemy unit that I can fire at, but isn't highlighted?

Is this a glitch? Hardly a hidden unit if it isn't highlighted, but can be located?

Thank you,

Pat