I had successfully used 3G/UMTS/CDMA connetion on my laptop on Madriva
2007 setting up
/etc/ppp/peers/umts adn /etc/chatscripts/umts
modprobe usbserial vendor=0xhhhh product=0xhhhh
pppd call umts

I'm currently trying to set it up on CentOS 5.2 for a week or more and:
It's getting connected but connection doesn't really work. When I ping
to google.com, I get "Unknown host".

I've got same result trying it on fresh installation of Mandriva 2008.1...