I was getting the same error. This was the problem on my system:

Installing the Java SDK does NOT replace /usr/bin/java with the Sun version. The /usr/bin/java on my system (Mandrake 9.0) was Kaffe (the Open Source Java-compatible VM). I did a

find / -name "java"

to find my java binary in the SDK subdirectories then replaced /usr/bin/java with a symlink to the correct version
(ln -s /path/to/javafromsun/java /usr/bin/java)

The installer now runs correctly.