I just bought a tiny 12" iBook and compiled ECL on it. It seems that there were two problems in the latest release:
(i) The fixes on the linux platform to avoid name clashes, caused some problem on OSX.
(ii) Most important is the fact that the 10.3 seems to include a flaky (at least not good enough for ECL) dlfcn.h header, which caused ECL not to use the OSX standard functions for loading FASL files.
Both problems have been fixed, and now ECL seems to pass Paul's test suite with at least as many bugs as in the Intel ports.