performance issue with new version

I’m making a project using panda3D.
Today I updated the Panda version. I was using to the new one (panda3d-2004-05-21A to panda3d-2004-07-16A). I just changed the imports to fit the new standards, but for my surprise the performance dropped a lot.
I use a P4 1.6 GHz with 512MB of RAM and a RADEON 8500 (64MB).
Did anybody has the same problem or is there somthing else I need to do to adapt to the new version?