Here are the steps to reproduce the bug:

1) create a project with several main classes.
2) add a configuration for every main class (project properties -> Run) so that switching between classes is made simple
3) start monitoring one class (monitor or memory, cpu does not have this bug)
4) try switching configuration
5) notice the error message "Cannot get exclusive access to /home/user/netbeans/project/private/config.properties
(probably opened for reading)." (path names may vary)

This is REALLY standing in my way. I have several non-trivial main classes (clients & servers) in my project with a few
runtime options. Therefore I created a configuration for every one of them. Now I wanted to profile them against each
other but after starting to profile (only monitor or memory) a server I can not switch to a client configuration...