ifconfig tun0 destroy error

[jronald]

1. ppp -ddial pppoe
ok

2. ping some url (terminate ping by ^C), ok

3. ifconfig tun0 destroy
error message appears continously even logouted, the message is like this:

Feb 4 15:27:47 ppp[785]: tun0: Error: ip_Input: deflink: wrote 52, got Device not configured.
Feb 4 15:27:48 ppp[785]: tun0: Error: ip_Input: deflink: wrote 56, got Device not configured.
...

What is the problem? and how to stop it?