Java 5.0 update 2 I hope?
Did you uninstall old java first?
You should uninstall old java, reboot, delete the java program folder, clean java stuff out of registry, install new java version, reboot, go into msnconfig and disable the startup item jusched (java update schedule) and then reboot again
That's probably the best way to do java, I'm thinking you got a registry conflict somewhere.