Good news for Netbeans 5.5 users - now the bug is fixed by the development team of UML Modeler pack.
Thanks, guys, now there won’t be any headaches of transfering
For those who need UML integrated in their Netbeans IDE, there are two solutions:
Working on one of my projects, I had to create some UML diagrams, not only for submitting it to the supervisors, but also for tracing the process of software development, and analysis stages.
I was really amazed trying to install new UML Modeler Plug-in for NetBeans IDE and seeing a nice shiny window:
“You can install the packages, but you won’t activate them!”
Just because of some dependencies incompatibility, their official website offered you a partial product: “Watch, but don’t touch!”
Hopefully, the development team decided to include some of those necessary plug-ins in the main part of NetBeans 6.0 version, so there would be no need of installing it again. From now on, I’ll have to switch to ArgoUML to finish up the stuff and patiently waiting for bug fixes of module dependencies 
Working on the Software Engineering diagrams and digging through different books, I’ve found a nice quote, which can be applied not only for UML:
Anything humans do well they do by taking tiny little steps and then evaluating what they have done. The things that
humans do not do well are things that they do in great leaps.We desire to create useful uml
diagrams. Therefore we will create them in tiny little steps.
It was taken from the book of “UML for Java Programmers” by Robert Cecil Martin .