unity can't load native dll

I have a weird problem with Unity not being able to load an unmanaged dll i put into the Plugins/ folder. I mounted the Process Monitor and noticed, that at first the DLL is accessed successfully. Then there's one unsuccessful attempt to create file at the same path, but with extension .la instead of dll. And this is followed by many attempts to read the dll at incorrectly generated paths, such as C:\Windows\system\libE:\Projects\dlltest\Unity\Assets\Plugins\mydll.dll, failing indeed. These paths include destinations where any application would commonly search for dlls, defined in windows global variables. The whole thing repeats many times, tracing stack to calling MonoBehaviour.Awake().

Now the weirdest part is that the project works for everyone in the team but me. We all have same versions of Unity installed.

I even tried to copy my plugin dll to windows system folder, no success