Due to the fact that some of the FaxMan .Net components are built using managed C++ and are mixed mode assemblies by default they will not load into an application built for the the .Net 4.0 framework.
To resolve this you just need to add the useLegacyV2RuntimeActivationPolicy attribute to the startup node in the app.config file like this:
<startup useLegacyV2RuntimeActivationPolicy="true" >
Once that is added to the app.config file for your executable then the ImageMan components will load into your .Net 4.,0 application.
* Please note that future versions of FaxMan will include .Net 40 compiled components eliminating the need for this extra step.