That sounds interesting. Please let us know how it works in the long run once you get more time. I would try it here but I have all 4 serial ports in use with other equipment.
The old ActiveHome 1.42 with CM11A connected via USB->Serial adapter has been running now for about 15 hours under Windows XP with no evidence of disconnection or other problem. It was left on overnight so the PC may have been "sleeping" for most of that time.
My testing has been limited to clicking the icon for a lamp module and observing that the lamp connected to the physical module turns On and Off, and verifying that I can reset the interface clock.
The PC used is an IBM ThinkPad laptop running Win XP Pro SP2. This PC has no RS232 serial port so there's no way of knowing whether there would have been a problem with direct serial port connection.
I used the no-name USB->Serial adapter I had purchased from Sewell (http:www.sewelldirect.com) in early 2004 which has a Prolific chipset. I understand the unit they currently stock has a Prolific chipset which has been upgraded from my model. According to Device Manager, Windows assigned the serial port as COM4.
Note: ActiveHome's Configuration>Preferences shows COM4 selected, however all ports except COM3 are greyed out. If I clicked on COM3 I don't know if I would be able to get back to COM4.