R 2.5.0 MAC OS X version

Please accept my apologies if this was addressed before, I could not 
find any solution so I am posting my question here.

I am having a lot of difficulties with installing and developing R 
packages with the latest version of R 2.5.0. I am using a MacBook Pro. I 
never had these problems with the previous versions of R. I think part 
of the problem is caused by the GNU Fortran 4.2.0 or my lack of knowledge...

If anybody else had similar problems and found the solution, please let 
me know.

Best.

Recai Yucel, Ph.D.
Assistant Professor of Biostatistics
Biostatistics and Epidemiology
UMASS-Amherst