thank you for the information.
I've solved the problem and understood why that error:
in our implementation of Vault Collaboration 2011 we developed more than one JobProcessor handler for our businness.
some of them are hosted inside the same .NET assembly, now with Vault Collaboration 2013 it seems to be unsupported because only one class need to be exported from a .NET assembly.
Maybe I've missed this feature from the "What's New" SDK help so I was a little bit surprised about this change also because the Exception being thrown is too generic to gives the exact direction to investigate on.
Thank you in Advance