$reference problem

[II./JG1_Krupinski]

Okay, I have tried to work on my library in a few weeks. But something has happened with the $reference directive.

Now this was working, but now it suddenly doesn't without anything different.

my reference is
//$reference parts/Adlertag/Adlertag.DataAccess.dll

My dll is here
C:\Program Files (x86)\Steam\steamapps\common\il-2 sturmovik cliffs of dover\parts\Adlertag

The dll name is Adlertag.DataAccess.dll

I get the follow error, only on exit from the server.

System.IO.FileNotFoundException: Could not load file or assembly 'Adlertag.DataAccess, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. The system cannot find the file specified.

I dont know what the heck happened. Can anyone shed some light here? I've been working on it for a few days without any headway.