liudr:
Great! Thank you Ray. Worked as you described.
I routinely prune my P&P USB com devices. Since I have started doing this, the 32U4 pro-micro boards seem to work consistently all the time under Vista. Also, when working with my Trinket clones or the Digispark t85, pruning seems to make for a consistent experience.
Also, this is a nice thing to do before teaching a beginner Arduino class... all students have the same serial port number! Matches documentation, overheads, etc.
Ray