Oh I should point this out... that libGLw.* shows up in a slightly different location for the 10.5 SDK.... (inside X11 not X11R6 as it does in the 10.4 SDK)... don't know if that helps at all...
ls -l /Developer/SDKs/MacOSX10.*/usr/X11/lib/libGLw.*
-rwxr-xr-x 1 root wheel 18968 Oct 12 2007 /Developer/SDKs/MacOSX10.5.sdk/usr/X11/lib/libGLw.1.dylib
lrwxr-xr-x 1 root wheel 14 Apr 12 19:42 /Developer/SDKs/MacOSX10.5.sdk/usr/X11/lib/libGLw.dylib -> libGLw.1.dylib
