The opening of the file dialogs of most of my Java apps (excluded JEdit, Eclipse) became really slow (10 seconds). I supposed the network-drives, virus-scanners etc. to cause the problem. It turned out, that Jars/Zips at the desktop (on windows...), cause the slow-down. After cleaning my desktop, netbeans 5.5/6 and other Java apps became fast again.
Like in real life, mess on a desktop slows down the performance...
[Thanks michael bien for the solution, I asked many people at workshops, projects, conferences, but my young brother knew the solution :-)]
NEW: Online Workhop Effective WebApps without Frameworks is also coming to: MUC Airport.