Yep, me too. I've been dealing with it for a long while. saw your post a few times while looking for the cure.
I SUCCESSFULLY tried this after not finding help...
Launch MCC (configure my computer)
Enter root password
Select Network & Internet
Select Remove a connection
Make sure eth0 is selected and press Next
This will remove eth0, sit0 and ppp0 from Network Monitor.
Now...
Select New connection from Network & Internet
Choose connection type (mine was ADSL) and press Next
select eth0 card and press Next
Choose type (mine was PPPoe, cable might be DHCP or PPTP) and press Next
verify DNS info and press Next
Start connection on boot, restart network (Next, Next, Done??)
Launch your browser.
At this point you should have only eth0 and ppp0 in your network monitor.
sit0 is a wrapper for ipv6 within ipv4 packets. (or something)
PS- if this fails for you, I can be of no help fixing it.
Perhaps a pro could go through the steps for us just to prove that it does not break anything and let us know.
when I was done I rebooted in record time. eth0 was up before I could read the text that was scrolling by during boot.
Good Luck.