"Couldn't find interface ppp0"

I've installed RH9 on my IBM R40 laptop and on my wife's Dell 333 desktop. Setting up her computer for Internet use was easy. Doing the same thing on my R40 however hasn't worked.

I've tried two drivers for the Winmodem, both of which worked fine (I uninstalled the first one and I'm now using the one recommended by IBM). Dialing in isn't the problem; staying connected is.

The modem dials up using kppp, but as soon as I'm logged in the connection dies. I get such messages as:
"Couldn't find interface ppp0: no such device"
"Kernal supports ppp alright."
"pppd: This system lacks kernal support for PPP."

pppd exits with a return value of 4 which indicates that the kernal doesn't support ppp.

/usr/sbin/pppd generates garbage, so I'm assuming that ppp indeed has kernal support.

Wvdial doesn't do any better than kppp.

I've tried just about everything that I've found posted on the net, with no improvement. Am I correct in assuming that my problem centers around ppp0? How do I get ppp to work? I'm new at Linux, so please be explicit in your instructions.