bootstrapping gcc from gcc fails but from sun cc succeeds

[kamaraju kusumanchi]

I am working on a Sun Solaris 2.8 machine. It comes with Sun C
compiler cc (5.5, 2003/03/12). Using this cc, I was able to compile
gcc 4.4 20081107. However, I was experiencing some stability issues
with it. For example, valid fortran code was producing internal
compiler errors  http://gcc.gnu.org/ml/fortran/2009-01/msg00178.html .

So, I tried updating gcc 4.4 20081107 to gcc 4.4 20080109.
Bootstrapping gcc 4.4 20080109 from Sun's C compiler works. But
bootstrapping gcc 4.4 20080109 from gcc 4.4 20081107 fails with an
internal compiler error
http://gcc.gnu.org/ml/gcc-help/2009-01/msg00109.html .

Could someone please tell me how to debug the problem further? How
does one go about debugging "internal compiler errors"? I have access
to dbx but no gdb.