Epoxy resin will sometimes turn cloudy and possibly form into crystals.  This is usually the result of exposure to cold temperatures.

Don't throw it away! 

The solution is to warm the epoxy resin to dissolve the crystals. Place the epoxy bottle in a pan and fill the pan with water heated to around 100 degrees F.  The crystals will dissolve should not return even after the resin is colled back to room temperature.