Gardening and Horticulture - why are the leaves curling?

Hi! I recently got a bonsai orange tree. A couple days after bringing it home, the leaves started curling. It's been that way for a few days now. They don't seem to be dropping off or drying up, just curling. I was wondering if anyone would be able to tell me why this is, and how to fix it? Any help would be appreciated. I've been following it's directions for water, sunlight, soil, etc... I can't think of anything else.

I have some pictures of it, if they help...

http://www.davanthegeek.com/posts/orangetree.jpg

http://www.davanthegeek.com/posts/orangecloseup.jpg

It may be simple transplant shock. You know, a new environment with different levels of light and humidity. I had one of them for 30 years. They do fine if you don't over water them.