What does this mean? "osascript: Please update this scripting addition to supply a value for ThreadSafe"

You installed SIMBL, a tool for patching applications at runtime. Mac OS X isn't happy that SIMBL doesn't declare whether its event handlers are thread-safe.

You can find an explanation for this issue here:

This is a dopey cosmetic issue -- the warning is 100% spurious.

The event handler used in Snow Leopard is correctly labeled as thread-unsafe. The problem is that this warning is about the event used for Leopard - which is completely unaware of thread issues. I can't figure out how to get it to be backward compatible and stop complaining, so I'll let it complain.

Based on my understanding of the source code, you can try editing the Info.plist in the SIMBL bundle and remove the following from it:

<key>SIMeleop</key>
<string>InjectEventHandler</string>

It's the Leopard-specific event handler (leop).

Thanks for all the info.

I went to the developer's website and updated SIMBL to the latest, and all is good now http://www.culater.net/software/SIMBL/SIMBL.php

The latest SIMBL installer also contains an "uninstall SIMBL" app, should the need arise.