Weird Connectivity Problems after upgrade/install

[Jason Greenwood]

Hope someone can help me out here.

Over the weekend I installed Mandrake 9.1 on a spare partition. I did 
this so that if Cooker broke something major, I had a spare stable 
system to boot into. All went well and I setup /home to be shared 
between cooker and stable. All went fine and I could boot either install 
having access to all /home stuff. I also upgraded my Cooker install to 
get the latest kernel and a few other bits and pieces. The problem is 
that now (after configuring my external modem) that I cannot connect to 
the net with EITHER install. It tries to connect but immediately after 
it says "logging onto network" (I use KPPP), the conn dies and it 
redials. I have NEVER had a problem with this modem and it is 
autodetected by linuxconf just fine. I checked in /var/log/messages and 
it says something about an invalid netmask??? I didn't set up a netmask 
and I am at a loss to find any reason for the problem.

Ideas??

Cheers

Jason