Gingko Biloba Seedlings Still Sticks in Late June

I have grown these from seeds provided by you two years ago and last year they were about 8 inches tall. I am a little worried this year as they have done nothing as of yet (Still sticks :( ) Have these ever been known to skip a year staying dormant or did these not weather the winter here in new england and died.
They are potted and were buried in mulch and removed about 2 months ago when the last frost cleared.
I have 5 of these that are doing the same thing - One given away as a gift is doing fine.

If the seedlings have not leafed out by now then they are likely to be dead. To be sure cut the stem on one and look for dry brittle tissue that is brown, black, white or yellow. An absence of live-looking green or yellow tissue is a sure indicator that the seedling is dead.
If you see live green tissue then the cut seedling, at least, was alive but unfortunately the cutting process probably killed it. The other seedlings however still have a chance. I have not seen seedlings go into an extended dormant period that extends into the warm summer months, so I think that the possibility that the seedlings still have some life in them is remote.
What could have happened? Well, the past winter was much tougher than the one before in the U.S. northeast. It does not surprise me that seedlings that made it through the 2001-2 winter did not survice the 2002-3 winter. Although ginkgo is rated hardy to zones 4-9, at the seedling stage it is more susceptible to hard winters in regions at the low end of their hardiness range. A heavier mulch might have helped get through the past winter – but there is no guarantee of that.