envelope.com refusing to protect specific DLL

Our automated build process generates the protected version of our .NET 4.0 application.

Up until a while back, this worked fine for the DLL in question, and we got our dongle protected software generated.

However, recently envelope.com refuses to protect one of the generated by the buildserver. I am able to generate a build of an older release, and have this come out dongle protected, however, so I assumed the newer DLL had a broken dependency of some description.

The error message is rather vague and cryptic, and only says the following:

1. [09:04:07][Exec] INFO: .NET - Starting Protection Process - C:/PATH/TO/THE/FILE.dll
2. [09:04:07][Exec]
3. [09:04:07][Exec] WARN: New methods were found in the application. Envelope will use the settings specified in the project file to protect these methods.
4. [09:04:07][Exec]
5. [09:04:07][Exec] ERR: .NET engine called with wrong parameter: C:/PATH/TO/THE/FILE.dll (2002)

I have tried updating our referenced resources the project generating the DLL, diffed the working and not working .csproj-file and verified the only changes are additions and/or removals of .cs-classes, and the removal of a DLL of a library no longer used by the application.

Further more, I am fully capable of using the DLL unable to be protected by Sentinel when generating an installer for an unprotected version with Install Shield, and the program runs without errors when installed with said installer.

I was hoping you could help me shed some light on the 2002-error, as google does not return anything meaningful as far as I can see.