i have done some more tests.
I created a new netbeans application in NB 6.5.1 and added only the Project API's and the ones they are depended on, when running this application the project tab does show in the Eplorer mode.
When repeating this in NB6.7, the Projects tab does not show in the Explorer Mode.
Any help will be appreciated.
I did log a issue regarding this matter
http://www.netbeans.org/issues/show_bug.cgi?id=167885
To be truelly honest, any feedback will also be appreciated.