Script library written in Java has been compiled with no error, but it cannot be saved?

In database, I have one script library written in Java. I did project configuration and assigned NCSO.jar in library.

I compiled the library and it looked good. But when I tried close the tab, it asked me to choose save and close option. SO I chose the option and closed tab.

But next time when I opened the library, it showed compiling error, then I saw NCSO.jar was disappeared from project libraies, so I added it again, and saved and closed the library, but the problem always existed…

What should I do to saved the successfully compiled java script library??

Please help.

Subject: Anyone can help?