[R-SIG-Mac] X11?

[Parlamis Franklin]

I installed R from binaries, using R-2.1.1.dmg.  I also installed  
R.app 1.12 but I cannot recall where I got it from (I assume it was  
in the aforementioned binary, because I do not recall building  
anything from sources).

When I open R.app and run a source("~/somefile") command to read in  
code from a source file, I get the following warning:

         Warning message:
         unable to load shared library '/Library/Frameworks/ 
R.framework/Resources/modules/R_X11.so':
           dlopen(/Library/Frameworks/R.framework/Resources/modules/ 
R_X11.so, 6): Library not loaded: /usr/X11R6/lib/libSM.6.dylib
           Referenced from: /Library/Frameworks/R.framework/Resources/ 
modules/R_X11.so
           Reason: image not found

I also get this message when attempting to run other commands.  The  
file "R_X11.so" is on my system, but the file "libSM.6.dylib" is not.  
although there are plenty of other files, including one called  
"libSM.a", in the referenced folder.

I think I may have installed xCode after the R installation, and I do  
not recall ever installing the X11 server from xCode or the fortran  
compiler often referenced in the documentation, for that matter.

I have tried reading through the Wiki, but much of it refers to the  
source build, and it is not clear to me what steps are handled for me  
in the binary distribution and what I still need to do.

Any advice would be appreciated.