help with ppp!!!

i'm trying to configure ppp with suse 7.1 ppc but it seems not working in any way i use a isdn terminal adapter (zyxel omni.net lcd) connected via serial port to a wallstreet powerbook, i tried with yast but also after resolving the "cannot locate module char-major-108" it doesn't work kppp tells kppp: interface is down after starting pppd and wvdial disconnects after few seconds without giving any error pls help! leonardo