In Terminal, run the following commands:
$ su root
$ cd /
$ cd System/Library/Frameworks/JavaVM.Framework/Versions/
$ sudo rm -rf CurrentJDK
$ sudo ln -s 1.4.2 CurrentJDK
After executing the above mentioned commands you should be able to install QLA.
[kirkmc adds: I haven't tested this, but there's always a risk in removing anything rather than backing it up first. So at the rm -rf command, I'd suggest making a copy of the directory with a different name.]

