ah yes i had a problem with the newest stable of firebird myself. The problem lies in the differnt forms of gcc.
i cannot remember exactly how to fix it (enough to do a "how-to") but i can tell you that when you dowload the jre there is 2 verisons of libjavaplugin_oji.so. One is in one foler, and the other is in another. You just have to do make the symlink to the correct one.
i found the my anwser at the firebird forums at
i hope that helps you. If i was on my computer i could give you the correct file location, but alas, i am at school.