Previously, we reported on problems with making connections with US Robotics modems. At the time, it appeared that the problems were entirely software-based, primarily with the modem scripts. However, Darin De Stefano reports that US Robotics has "announced they had a bad ROM set in some of their modems which would not allow dialing out. I had this problem and returned my modem. It was fixed and works fine now." (Darin thinks there was a mention of this in MacWEEK awhile back, but I could not locate this.)
Apparently it only affects some communication software. For example, Darin had it with MicroPhone but not PPP.