what does 'Object could not be created because abstract method has not been implemented'?

kwmkwm

I'm in AX2009, wrote a class that work in single AOS environments but not in our Production environment. The class is called by Product Builder to supply defaults per warehouse, works fine except in the only environment that matters. We think it was working for 2 weeks, but now the model cannot be compiled without the following error without the 'Object could not be created because abstract method RunBase.unpack(container) has not been implemented'.
Can anyone tell what is happening?
Kevin