I'm using Arduino Uno and Windows7. The port for the arduino board is "COM3" on my system. It is available in windows' system control panel > device manager.
My problem: But in the IDE only COM1 is available in the serial port menue.
Note: Actually COM3 is available, so I'm able to work with it for a while, but after uploading some sketches the menue entry COM3 somehow vanishes, so that only COM1 remains (I can't use of course). I have to reboot in order to continue my work.
I must admit that I disconnected the USB cable and then re-pluged it in (COM3 entry in device manager remains available). Maybe this is the cause?