Any ideas out there for me? COuld really use some guidance. 

Thanks, 
Mac

Waiting for a full cure before sanding is definitely the first thing to do. Once it's cured, wash it with plain water and a scotchbrite pad and follow up with a denatured alcohol wipedown. That will get rid of the spots if they're amine blush or dust trapped in micropits. If they still persist, it's time to sand.

Any chance of a picture?

Laszlo

Yes, Laszlo's suggestions are well worth keeping in mind when working with epoxy. I can only add that epoxy can melt when subjected to localized heat generated by using power sanders too aggressively. What you may be seeing is potential evidence of this having happened.

If you see opaque areas left after sanding, and you're sure you waited long enough before sanding that the stuff has cured fully (time & temperature dependent, also the brand of epoxy used and choice of hardener if you have one) those opaque spots should sand off fairly easily. I'd try going after them with a hand-sanding block before resorting to power sanding should they prove to be stubborn. Or scraping with a cabinet scraper or single-edged razor blade if on a flat-enough surface.

~ 140°F is where epoxy begins to soften. That's quickly reached at the edges of disc-style sanders when they're leaned on too hard, or tilted so the discs aren't flat to the work being sanded, or simply being run too fast.

This characteristic is worth paying heed to when it comes time to choose a finish color - light is better than dark for surfaces exposed to direct sun when in use. Same also for storage conditions when not being used – try to avoid areas where direct sun will be shining on your work for extended periods.