My DD still cries when I drop her off - she's been at the nursery for a year now!!!
I find she's better if I drop her off, tell her i'll be back later, and just go - I don't hang around.
They tell me, and other moms do, that she's stopped crying by the time I've got back to the car!
I also find that if she misses a week (if we go on holiday), then it sets her back a bit, so i try and make sure she goes evry week, on her 3 days, even if I'm at home for some reason.
She has a dummy and a muslin cloth for comfort - the nursery say this does help her - i'd like her not to have them, but if it's helping, then that's the most important thing to me.
They also suggested that i took in some photo's - they laminated them for me, and they show he rthe photo's when she gets upset - this also helps apparently.
She is very clingy to the staff, and they are aware of it now. My DD would rather help staff with whatever they are doing 9even sweeping the floor), than play with toys or other children - the staff are really good, and let DD do what she is happy doing (they let her help).
It is really difficult, but I know that nursery is doing her good - if she didn't go, school would be a nightmare!!!!
Good luck, and I hope it gets better for you, and your DC.