Posted: 08/05/2013 at 14:48
Given the March and April we've just had it'll have been frozen solid just when the sap was rising to feed all the newly unfurling leaves. This can be fatal. It was for 2 of mine last year and did a lot of damage to a hamamelis and some roses.
You're just going to have to be patient and give it to mid June to recover. If it has produced new foliage by then you can prune out all the dead wood to just above those leaves. If not, it's a goner.