USB modem doesn't run on opensuse 11.0

I can’t make my conexant V.92 D400 usb modem work. when I run kinternet, first it shows an error message like this:
“smpppd is not running or you’re not a member of dialout group.”
Then I run smpppd as root and kinternet consents to run afterwards. Then it comes to add settings in YAST/modem. There is a default device name: /dev/ttyACM0. So I choose it everytime and go on with the installation process. But after finishing, when I try to dial a number with kinternet, the following message shows:
“pppd options error (exit code 2)” or something like this.
One of my friends who is good at linux showed me there is no ttyACM0 in /dev section. He couldn’t make it run after a few tries, but was convinced this problem is caused by udev(which I barely have an idea of).
Can anyone help?