Ed, thank you for pointing to problems in QVTO.
The problem that exists in M4 is that when Eclipse plug-ins
have cyclic dependencies and simultaneously contain incorrect
import statements, this produces in QVTO M4 StackOverflow
The reason this happened is that a lot of new functionality
were implemented for QVTo M4 build. Beside others the Bug
433937 "Add support for libraries from other projects" created
As mentioned, the problem is already fixed.