I am running under Win8.1 and having a strange USB com problem that I can not solve. After establishing a connection to a USB Arduino Leonardo and successfully installing its driver, Win8 looses the port but shows it as in use. Here is the context:

After successfully communicating with the microprocessor, I monitor the device manager. I see COM8 under Ports(COM&LPT).
I go through a modify microprocessor code,upload and run cycle several times with no problem. The COM8 entry in DM stays the same. Then, I perform an upload and the COM8 entry disappears.

At this point, I have lost connectivity with the arduino. However, COM8 is listed as in use but appears nowhere in the DM. Eventually, after a lot of fiddling (uninstalling the device driver, plugging/unplugging the USB cable, ...) I get COM8 back. A little later, events repeat.

My (probably flawed) understanding of what is going on under the hood arduino-wise is this: the uploader (avrdude) kicks the leonardo into its bootloader by switching the COM port to COM7 and connecting at 1200 baud. It then reverts back to COM8. When this works, I see COM7 in the DM and the switch back to COM8 replaces it in the DM. When it does not work, COM7 disappears about 10sec after initiation of upload and COM8 nor longer appears in the DM but is still thought to be in use by Win8.

I'm guessing that Win8 does not like the port switching activity going on "behind its back".

Although I can eventually get things back to "working order" as mentioned above, the process is so tedious and problematic that it makes software development on the attached arduino impossible.

I am hoping that there is some work-around that someone knows about.

Thanks in advance for any ideas.