Hi Matt @LBnewbie, Chris @chris101,
I have exactly the same ! 😢
After editing an .ino file or uploading, it takes appr. 1 minute and then the com port is disconnected in the IDE. I am using Windows 8.1 (and recently 10) and the latest version of the official IDE.
The com port (including the Arduino Leonardo reference) is still visible in the list under tools-port in the IDE menu, but I must select it every time again before uploading.
Makes me a little crazy !
I think it might be a Windows issue, it started for the first time when I started using 2 different Arduino types.
I own an (old) Duemilanove which worked 100% OK, until I started using the Littlebits Arduino Leonardo.
Then my computer got instant amnesia. and could not hold the com port stable.
I am looking for a solution, but I canot find it. Anywhere......
When disconnecting the Arduino for hardware bit changes, the sequence of reconnecting is very important, else the computer will never see the Arduino.
Disconnecting: 1: USB, 2: Bit power.
Reconnecting: 1: USB, 2: Bit power, check IDE COM port, OK.