I had a DV2000 and one of the slots just wouldn't work, exactly how you describe, put some ram in...nothing.
Try the new stick in the original slot to see if its ok.
Whats the max RAM for that laptop, can't remember.
Unless this is starting, I ended up baking mine and it totally wasted it. http://www.youtube.com/watch?v=PhxOVh2sbl8