Don't Try this at Home: Eclipse 3.1 Install by Replace

This morning, I decided to upgrade to Eclipse 3.1. To save my time, I decided just to replace files in my old Eclipse 3.1M6 directory - after all, there is no big difference in versions...

Big mistake!

After the "upgrade", I spend almost an hour trying to figure out what the message: Failed to execute runnable (java.lang.NoClassDefFoundError: org/eclipse/core/internal/resources/mapping/ResourceMapping) means. And here is my advice :-)

1. After stopping Eclipse, rename the old Eclipse directory to something like eclipse.old
2. Make a clean install of the Eclipse to a newly created directory.
3. Enjoy!