That is the path where the AFSDK will put the DC Plugin assembly when it loads it from the AFServer. It will then attempt to load the assembly from this directory.
The error message indicates that there is a problem with the assembly or one of its dependencies. It could be an issue with attempting to load a 64 bit assembly in a 32 bit application or running as a 32 bit application and attempting to load a 64 bit assembly. Is you DC Plugin compiled as AnyCPU or does it reference any other assemblies that are not AnyCPU?
The problem was exactly in the AnyCPU assembly setting, the DC is working now.