cestlavielife is right - lots of kids take time to settle at nursery.
If you cannot change what you think is the cause (agree it's not helpful of nursery to lay blame) then you need to look at other things.
A friend of mine's baby was traumatised by his nursery's doorbell - odd but true. So the nursery changed the 'ring-tone'.
That's an odd example but what I mean is, you really need your nursery to buy in to this too, to help.
Are you 100% happy with the nursery? We all know how perceptive kids are - they're like killer dogs, they can smell your fear!
Seriously - if you're approaching nursery with trepidation (and who could blame you - knowing it upsets your child?) but they'll pick up on that. They'll sense your fear/concern and even if they don't know what it is they'll expect something bad is going to happen - because Mummy's worried.
Try to be really positive - ostentatiously so. Talk positively about nursery before and after you drop them off there. Silly things that they can look forward to like a special toy, friend or food they have there.
Even though they're very little explain it to them and explain when you'll be back to collect them. Obviously they have no concept of time so "At 4o'clock won't mean much" but "After your nap" or "After dinner" eetc. might help.
Also, get the nursery to help with routine. Your child won't be the first (or last) they've had that won't settle. Get them to ensure the same carer always 'collects' your child from you - in a happy "yay" way etc.
And finally the firework test - never, ever go back. Once you've left, stay out until collection time. If you go back it just confuses them and/or torments them. Good as nursery is it's not as good as Mum/Dad - it's like taunting them with their favourite toy if you linger or go back.
It's heart-breaking to walk away - but it really is for the best and definitely worth it.
My son took a while to settle at his nursery - but now when I drop him off he runs into the room SO excited and happy - it's practically me getting a bit moopy at the door! .... .
Daddyblog
My blog: daaddy.wordpress.com - a silly look at life as a 21st century Dad