So i called EqualLogic support, they advised to just re-install a new appliance by downloading the complete ISO (not the upgrade one).  Apparently something in the Java machine is broken,... so i just did as they advised as i had not so many scheduled jobs set in VSM. You can also make a backup of the database and re-import it to your new installation.
Hi, I upgraded VSM from 3.5.2 to 3.5.3 and then also upgraded vSphere from 5.1 to 5.5 and now the VSM plug-in is gone. On the console when I boot the VM I see this[IMAGE]
VSM not working after upgrade