This new compile error was driving me mad! My project used to work, then I upgraded to a newer version of ECO.
There were 3 projects using an EcoSpace, 2 would compile but not the 3rd. In the end the solution was simple but annoying to track down so I thought I'd mention it here just in case anyone ever strolls across it and finds it useful.
In my licenses.licx files for the 2 projects I had the line
but in the project that was failing somehow a strong name had been used, even though I originally entered it manually! Changing it back to the weak name fixed the problem.