Netbean 6.9.1 library problem

I have just upgraded to Netbeans 6.9.1 from Netbeans 6.8 and the following problem arose what was not there in Netbeans 6.8:

I have an own project jar (let's name it alma.jar) that is used in several other project. Some beans from alma.jar also appears on the Palette. alma.jar is in the dist folder of the alma project and all the other projects see it/us开发者_开发知识库e it. Since alma is continuously developed it is always added with Add project.. so when an other project is cleaned and rebuilt alma.jar is also rebuilt. However from Netbeans 6.9.1 clean is not working as Netbeans 6.9.1 locks alma.jar, so it cannot be deleted even from the filesystem (I am using Windows XP). When I first delete alma.jar and AFTER THAT I start Netbeans 6.9.1 then I get some warnings during the startup when a form is open that is using alma.jar's classes appearing on the palette but otherwise I can clean and build correctly.

How could I avoid the deletion of alma.jar before Netbeans startup?

This is not a solution just a workaround:

If you turn on 'Compile on Save' setting of your project, you can avoid most of the clean and build processes.