There are innumerable variations on this (take a look in comp.os.linux...).
A VERY common mistake is that you have mistyped something in your
scripts. The only thing to do here is to make sure you are logging the
chat conversation between you Linux PC and the server into your syslog
(/var/log/messages) and then go through this line by line to make
sure there are no mistakes.You may need to dial into the ppp server manually to check
things out again.
You need to check the log against the actual prompts very carefully -
and bear in mind that we humans have a tendency to read what we THINK we
have typed - not what is actually there!
Take our 
