If the last time Apple publicly posted sources to launchd was when Snow Leopard shipped, it may be that there were no critical bugs in launchd that were worth fixing in Snow Leopard software updates, so none of the post-Snow-Leopard updates to the Darwin sources would contain any launchd changes.
When Lion ships, you can expect to see a huge new drop of Darwin sources based on Lion. You may find that a lot has been going on behind the scenes over the last 2 years. Or not. But given that Apple has said Lion will ship sometime this month, your question might be 2 weeks premature.
You must specify the full path in ProgramArguments. Things which your shell normally expands, such as ~ and * are not expanded by launchd.
After making those changes, this LaunchAgent worked for me.
You said you made these changes, but it didn't fix it. It is possible that you did not reload the LaunchAgent after making the changes.
Troubleshooting LaunchAgents
You can check if your LaunchAgent is currently loaded by running
launchctl list | grep com.nocturnal.mcworldsBackup
If it is not running, you can load it by using
launchctl load ~/Library/LaunchAgents/com.nocturnal.mcworldsBackup.plist
If you make any changes to the plist file, you will need to unload it using
luanchctl unload ~/Library/LaunchAgents/com.nocturnal.mcworldsBackup.plist
You will then need to load it again, using the command from above.
If you want to force the LaunchAgent to start now, instead of waiting until 4:30, you can run
launchctl start com.nocturnal.mcworldsBackup
You can then list it using
launchctl list | grep com.nocturnal.mcworldsBackup
The first column of the result is the PID of the process, if it is currently running. The second column is the exit code returned last time it was run. Use this to check if it ran properly. If not, the error message is written to /var/log/system.log.
Best Answer
There is an app Malwarebytes which is popular for detecting and deleting Malware. I don't know how this compares to Nortons but maybe its a viable option. The website,located here https://www.malwarebytes.com/mwb-download/, advertises a free version. The full application is available here: https://www.malwarebytes.com and also offeres a free version.