For those of you that may be wondering what this was all about, there is an excellent RMI tutoral at http://java.sun.com/docs/books/tutorial/rmi/TOC.html
This example worked with gcj as long as Sun's rmiregistry was being sued, but not with grmiregistry, which segafulted. The changes I made in gcj's serialization code mean that we have interoperability between Sun's RMI and gcj's, in both client-server directions. I haven't tried anything more elaborate than this simple test, though. Andrew.