This is now the second time. All my cuttings in the humidity bin seem to get 4-5 inches tall then the leaves start falling off. Of course the cutting dies soon afterward. The first round I thought I allowed them to get too wet, this time I have been careful about that.

Any ideas what is happening?

how wet was your soil mix? how was the root when you put them into the humidity dome? leaves falling off and your cutting dying typically indicate that the cuttings had rot or lost all the roots under the soil. too much water usually does that. then it will invite gnats and fun begins. 

could be several things but, typically, too wet like Pete said.

I was having the same problem using potting mix in 32 oz deli cups right after coming out of rooting box.  Roots would grow till i see them on the sides then suddenly they'd start rotting.  The soil was just damp and I did not water them more.  leaves would wilt, then drop and roots would rot.  I lost about 65% of all done this way.

I went back to using perlite/vermiculite for the cups and so far they are doing fine.  Have about 10 going and seeing good roots on the sides of the cups.

what was being used for soil mix? what was the composition?

I was using vermicile and long sphagnum moss in 20 oz cups. I have tried to be extra careful about watering, bottom only, and only when there was no moisture showing on inside of cups - usually every 7-10 days. But as of right now, all but 4 of my cuttings done this way have dropped leaves and died. Three of the four are so so looking, one looks strong.

Thankfully, after my first cutting fiasco I reserved at least one cutting of each variety and am trying the "old fashioned" way outside in loose soil. Maybe those will save my butt?

Also a side note. My Hardy Chicago looked pretty bad when I unwrapped it. The top 2 ft looked dead from freeze, but that was OK since I was planning to remove the top anyway to encourage lower branching. On a lark I took those 'dead' top cuttings and laid them sideways in a pot of good soil and covered them 1-2 inches. Just left them outside. Today I noticed that both are pushing leaves out of the dirt!

idea is to balance drainage with something to hold water. too much drainage and you'll have to water often. too little and things stay wet. perlite is good. sand works, but they are heavy and i can't tell when the soil mix is dried.