I just downloaded blender 2.49b onto my new mac (use PC before) and installed the required python 2.6.
After it worked fine for a day or so it now has difficulties selecting meshes especially when I try to ‘cut holes’ into some boxes. It only selects the first and then doesn’t find the other. Everything else seems to work fine - ah - it now has problems moving the cursor…
Right - so now when I click on the workspace it deletes the selected objects and the toolbar shows Dx: nan Dy: nan Dz: nan(nan).
I assume you are using OS X 10.5 or 10.6. Blender uses the python that comes installed as part of OS X (I believe it’s python 2.5.1). Installing other versions can cause dificulties, using yafaray for instance.