At first, check the version of your iDevice Manager. Click the info icon on right top. Please use only the latest version. Download: http://www.software4u.de/en/products/idevicemanager/default.aspx
If you have also installed the latest iTunes version, then check following path:
- C:\Program Files\Common Files\Apple\Mobile Device Support
- C:\Program Files\Common Files\Apple\Apple Application Support
- C:\Program Files (x86)\Common Files\Apple\Apple Application Support (only on 32-Bit Win systems)
- C:\Program Files (x86)\Common Files\Apple\Mobile Device Support (only on 32-Bit Win systems)
The last path does not have a iTunesMobileDevice.dll. If this file existing, then delete the file. Since iTunes 12.1 64-Bit is this file not longer existing in the x86 directory.
All the best