mianwei,
Sorry that you are seeing issues with Darkest Dark plugin.
The problem is most likely caused due to our plugins not having full write access to your workspace or the Eclipse installation.
Could you try the following and see if it fixes the issue?
1) Run Eclipse as an administrator.
2) Try a brand new workspace by using File > Switch Workspace and specifying a directory which does not yet exist, but which you have write access too.
If you are still seeing issues, then please share with us the OS and version details, Eclipse version details from Help > About Eclipse and the .log file located at workspace dir/.metadata/.log for further investigation.
Apologies for inconvenience caused. Please let us know how it works for you.
–Swapna
MyEclipse Support