I use Windows 7 64 bit. Having worked with Winmwerge (latest version 2.12.4), Then I can not disconnect the external USB.
Always appears the error: 'Can not stop the device' Generic volume 'because in use in another program'.
I have to restart the pc, because in Task Manager can not identify the process that locks the drives.
I realized that the problem was due to WinMerge for exclusion.
When not in use WinMerge during the working session, the problem does not occur.