And the modem is back online. The installer hasn't yet showed up, not due until 9:00-11:00, it was offline all day yesterday, until midnight when I went to bed. So this morning when I got up I checked, hope against hope, and it was working. I've kept the morning free and will wait for the installer, this is far too inconvenient to consider solved. But there's something about having him/her come here when it's working that rather undermines the point of it not working, hopefully they believe me....