Wow, Arisaemas are particularly difficult to ID. You need to know growing conditions, when the dang thing bloomed, how many leaflets, how the flowers are arranged on the spadix, etc. There are lot of photos and ID keys posted at www.aroid.org if you would like to take a shot at the keys. My first thougth is it is one of the species from Asia.

Here is a link that might be useful: Ray Herold's Arisaema Pages Archive is hosted by the International Aroid Society

Maybe you want to take a look at PDN's website, I trust them to ID theirs correctly. They have good pictures...

Evelyn

Here is a link that might be useful: PDN Arisaema page