We have desktop add ins developed in C#, and the add in references other assemblies. Occasionally, a user gets an error that the add in cannot find the dll specified (it's always the same dll), and the add in won't run the code. The dll in question is in the correct subfolder of the add in file. All I have to do to eliminate the issue is to rebuild the add in and get the new version to the user in question, but it's really an annoyance, for the user and for me. Any ideas on what might be the problem?