The arduino micro sometimes fails to show up as a COM port

It appears that the driver for the arduino micro fails intermittently. I get the error message "Windows has stopped this device because it has reported problems. (Code 43)". At the point I took the screenshot I had 3 arduino micros plugged into my computer, 2 of which showed up as COM ports and 1 of which shows as an unknown device.

The number of arduino micros that windows recognises has varied over time so I don't think that this is a hardware error.

I am running arduino 1.5.8 on windows 7 64 bit. I have installed the latest drivers available.(I attach a screenshot of me looking at the driver update).

Background: I am polling a pressure sensor over I2C and streaming the data back to a windows PC.