Dll Call Back problem only in Standalone version

Hi, I face a very strange problem when working with dlls in Unity, I have 2 different dlls, one is managed one, and the other one is not managed , the former register a call back to latter one, and receive some information from an external hardware in different time period,

I created a sample program in visual studio and tested both dlls, and I successfully retrieved info from hardware, I did the same test with editor and after solving some minor issues, I got system working very nice, even though the unmanaged dlls attach to Unity and I need to restart every time I am running the test, I created the stand alone version, but the application messed up, I am sure that both dlls are loaded and can call each other methods, as I am initializing the hardware by calling a managed function inside unity which in turn will call the correspondent c++ one to initialize the external hardware, and this part work very nice, but the registered call back method will never be called in this situation,

I really appreciate any help or comment on this issue,

Thanks, Brad,