For a variety of reasons that I won't go into we are stuck on Joomla 2.5.14 - and Virtumart 2.0.20b - we cannot upgrade.
Is it possible for you to provide a link for us to download an older version of ECC+ that is Joomla 2.5 compatible?
I understand that you would not want to "support" this old version - but I'd like to give it a go to see if we can stop virtuemart user registration spam.
If it does not work - I would not expect you to provide support if you did not want to.