Alright, a couple of hours later I had Mandriva running and almost everything was configured, I even got JDeveloper running everything, seemed to be a-ok. I noticed that during the installation process one of the first questions was "Do you want 3D desktop effects?" of course I do! and selected Metisse, boy was I for a surprise. Not only because Metisse provides cool effects but because it also bombs my VNC connection and I can't take a single screenshot that doesn't come black (??), so I switched to Compiz... and I was hooked, so nice, so shiny, so useful... everything seemed to work a-ok (riiight...), fired up JDeveloper to do some work and got a gray screen (wtf anyone?).
Thing is that there is a bug in Java (6429775), seems like jdk6 doesn't handle Compiz nor Beryl correctly. The odd thing is that it is supposed to be fixed since jdk6u1 build 01 (approximately 12/14/06) but many have reported the bug after that to be alive, with different OSes and apps (they even stated NetBeans is broken because of this bug), but no reply has come nor has the bug been reopened

So it is a sad thing that I must go back to plain-old desktop and wait for this bug to be fixed. Its sad, so sad. These are my settings in case someone is interested in keeping track
Mandriva 2008 (2.6.22.18-desktop586-1mdv)
Compiz 0.5.2-9mdv2008.0
Jdk 1.6.0_05-b13
JDeveloper (undisclosed version)