probably some .o-file is still lying around which is not deleted by "make clean". while Gem compiles (and deletes) only files that refer to the entries in Make.source, it links together all .o files it can find (jaja) you should run "./configure" (or at least "./makesource" after a "cvs up")
and i guess you are compiling HEAD ?
no time to dig into this atm ... i went back to 0.90 and added pix_mean_color, which fulfills my needs for now ...
t