http://blog.elitecoderz.net/category/development/java/eclipse-java-development/
The usefull information in this special case is: org.apache.commons.lang.exception.NestableError: Java Model Exception: Java Model Status [src/net/project/windows [in project] does not exist] for any reason, eclipse can not open a special file on the workbench. After several tries I found a way to solve this problem:
- Make a backup of your “.metadata“-folder (very important!!)
- navigate into the “.plugins“-folder located inside “.metadata“
- delete the folder “org.eclipse.ui.workbench“
- startup eclipse again and check if there is still everything you need