I've got the same problem. I just posted a similar message.
It looks like a bug related to Eclipse 3.1. I did not have any trouble with Eclipse 3.1M5.
Let's home the project admins will answer to our problems.
Please take the time to search the forum PRIOR to posting problems.
Just a simple scan of the thread titles would have pointed you to a dozen or so issues people posted about Eclipse 3.1 support post M5 (its been an on going topic for a month or more now).
Read those first.