Does the connection process reach the verifying username and password stage?
Yes :
Follow instructions for that error.
No :
Make a new dialer
Still not working ?
Check the network stack is correctly configured.
Still not working ?
What type of modem, if applicable try connection on kflex number.
Still not working ?
Re-install Dial up Networking.
Still not working ?
Re-install DUN again.
Still not working ?
Close down all background apps and try again.
Still not working ?
Extract rasapi32.dll.
Still not working ?
Problem with modem.