Yuri,
An additional response did not make it to the forum by accident. The problem is that the Spring license is new and cannot be recognized by a product as old as MyEclipse 5.
You could:
a) Use a more recent version of MyEclipse Pro – at least version 9 or higher with the Spring license.
b) Write to [email protected] with a link to this thread. They should be able to generate a separate professional key for your use with MyEclipse 5.
Sorry for the delay and hope this helps.