The Java 5.0 "missing installation instructions" are here.
But the error, "HotSpot not at correct virtual address. Sharing disabled." is another curiosity. I've seen this complaint a lot on the Apple boards, but no real solutions. A lot of fingers have been pointed at QuickTime updates, but I don't know whether that's valid. Some users have reported that using Pacifist with the latest Java 5.0 update resolves the issue.
I would first install any other updates you might need, then follow the steps in the "missing installation instructions" above, and then see if you still get the HotSpot virtual address error. If so, then Pacifist seems to be the next step.
"We're kind of on the level of crossword puzzle writers... And no one ever goes to them and gives them an award." ~Joe Strummer sscce.org
To use the J2SE 5.0 version of any command-line Java utility, such as java or javac, specify the full path to the J2SE 5.0 version of the command. This usually means prepending the command with the path /System/Library/Frameworks/JavaVM.framework/Versions/1.5/Commands/
So I need something like a startup script to set $JAVA_HOME, right?