Ha, my first proper handy hint (as opposed to sarcastic arsehole comments usually posted by me!)
If you should find yourself using mandrake 9.0 and an alcaltel speedtouch usb adsl modem, you may find, like I did that your connection gets a bit unstable/or it just won't connect properly.
I was connecting on boot, I could ifconfig as root and the connection would appear to be up and running, but when I tried to access anything I just got the "unable to connect to server" dialogue. Also, when I checked the connection in the "mandrake control centre", the connection was shown as "not connected", when I tried to connect, it would tell me that the connection had failed etc etc.....
The answer seems to be to edit the /etc/ppp/peers/adsl file, the system is probably giving you /usr/bin/pppoa3 -vpi 0 -vci 38 (these are the vpi/vci pair for those using BT lines from the UK) it should read:
/usr/sbin/pppoa3 -vpi 0 -vci 38
and you will need to include your log in details in the user line - leave the " " marks on both the lines mentioned.
I should also admit that I got this from the mandrake user board
it's not original thought on my part (I don't do original thought - just plagiarism)