Windows 'forgets' the com port

Hi - newbie here. Everything working fine coding and downloading to Arduino Lilypad using USB cable and COM8. But, if I do successive downloads without first unplugging the USB cable, then re-plugging it, I get the error message you would normally see if the cable was unplugged anyway. It's like Windows has forgotten the cable is still there, and has re-set COM8. Any help out there?

If you add the arduino to a different usb port, you get a different com port.

Yes but I'm not unplugging it - if I leave it plugged in and re- download edited code windows says it can't see the port. I then unplu and replug to the same port and it downloads - just once.

What do you have connected to the Lilypad?

Just an led and a resistor. It does the same thing whatever I have connected. Or nothing connected at all

Have you tried a different USB cable?

Does anything get noticably warm?

Have you tried the Lilypad connected to a different USB port? Or a different computer?

I only have one USB cable with the appropriate connector, but that was working absolutely fine on a different computer. I will try it on a different USB port. It seems that no-one else has seen this problem before, and it's liveable-with, so if using another port doesn't work, I'll just carry on unplugging and plugging to download my code every time, and curse Windows as I do so!