Multilink ISDN problem

I have a 3Com external ISDN modem, which I've been using with SuSE since before version 5.0. I always use wvdial with the setup command "AT S80=1" to configure the modem for multilink. A standard "ATDT xxx-xxxx" command links both channels into a single connection. Up through v6.4, multilink dialing has always worked right out of the box. With v7.0 and v7.1, however, only the first line ever connects. I know the problem is not wvdial, because the same thing happens if I use minicom and dial the ISDN modem manually. Anybody have any idea on what's happening? I really need to move up to the latest version of SuSE, but not if I can't use the web at full speed. Respond directly or to the mailing list, I always check both. Thanks, Sam