Rjb and Java 1.5

I’m trying to use rjb[1] to talk to some Java code compiled with Java
1.5 on OS X. I can run simple examples that only use Sun’s code just
fine, but when I try to run our code (compiled from within Eclipse,
if that matters), I’m getting the following error when I attempt to
import one of our classes:

(Unsupported major.minor version 49.0) (UnsupportedClassVersionError)

I verified that I built the RJB extension with the 1.5 headers, my
JAVA_HOME variable points to the Java 1.5 installation and when I run
java from the command line, it is Java 1.5. But the error I’m
getting looks like somehow Java 1.4 is getting dragged into the picture.

Anyone seen this error or have an idea how I might eliminate it?

[1] http://arton.no-ip.info/collabo/backyard/?RubyJavaBridge

Thanks,