I'm posting this just for a reference point and to make sure there's no wondering about whether the releases of Java after 7 update 7 fix/address this problem.
I just finished installing Java 7 update 9, deleted all traces of the CommCell Console GUI from my computer, re-downloaded the JNLP file - without making any changes to it before or after - and tried to open the application. The result: still not fixed. The newest version of Java does address SOME issues with JNLP files and the reading of tags but [apparently] not this one.
The fixes listed above are still valid and should still be used until CommVault releases some sort of patch/hotfix for this problem or until Oracle releases a version of Java that isn't sensitive to the "?" character.