Debugging makefiles.

I have sucessfully built and run R from source and I have begun to change some of the source files to help with my learning process. All of a sudden I recieved the following error on build:

building package 'stats'
all.R is unchanged
building package 'datasets'
all.R is unchanged
../../../library/datasets/R/datasets is unchanged
building package 'methods'
all.R is unchanged
make[3]: Nothing to be done for `RfilesLazy'.
building package 'grid'
all.R is unchanged
building package 'splines'
all.R is unchanged
building package 'stats4'
all.R is unchanged
make[3]: Nothing to be done for `Rfiles'.
building package 'tcltk'
all.R is unchanged
../../bin/R: not found
make[1]: *** [R] Error 127
make: *** [all] Error 2

I have just changed MkRules and some of the Fortran source files. I have not changed any of the Makefiles so I am not sure where this error is coming from or how best to trace the root of the problem. Maybe someone with a little more knowledge on the 'R' source structure and build process could help me out with a little advice here. If have tried the '-d' option but that is entirely too much debug information for me to digest. I just need to know where '../../bin/R' is needed and why it is not found.

Thank you.

Kevin