[PyMOL] atom selector problems

[Arthur Glasfeld]

I apologize if this has been covered in earlier threads - I'm new to  
PyMOL and was unable to find mention by searching the archive.

When using the center mouse button to select atoms on screen, I often  
(~50% of the time) find that PyMOL interprets my atom selection  
incorrectly.  Generally, it returns an identifier from the same  
residue, but sometimes returns an atom from a different residue as  
well.  I'm using MacPyMOL (0.99) on a MacBook Pro (intel chip)  
running 10.4.7 and a Kensington Turbo Mouse.  I've tried playing with  
the Mouse mode, and have had the same problem when I use the trackpad  
in single button mode.  I've managed to test this out on a Windows  
machine, and have no problem on that platform.

Is there something obvious I'm missing?  Any suggestions would be  
welcome.

Thanks,
Arthur