CasaDelGato,
I could not replicate the issue at my end.
Can you please answer some more details to help us investigate further :
1) Can you please share the Installation Details from MyEclipse > Installation Summary > Installation Details ?
2) Can you please share us the exact steps in detail to help us replicate the issue at our end ?
3) If possible can you please attach the sample project which contains the subclass of JLabel and the Form into which you are trying to drag in to ?