Here's a MacWorld article I ran across that has some tips for taking pictures of Christmas lights! I thought it was pretty interesting. There were some things in there that I would never have thought of.
Hope you might get some use out of it.
Taking pictures of Christmas Lights
Tom (... learning is good! Now if I could just remember.)
PS - Note that the article says "Holiday lights", not "Christmas lights". However, I refuse to be politically correct! It's too much work!