Re: Network doesn't work properly!
Network Mangler -oops, I mean Network Manager- as shipped with 8.04, unlike any other linux networking software I have ever seen, does not use /etc/network/interfaces and in fact iface entries in /etc/network/interfaces can cause NM to stop working altogether with that interface.
The default /etc/network/interfaces file in hardy with Network Manager installed has only these 2 lines:
Try changing your /etc/network/interfaces back to this, set Network Manager to defaults (roaming) and see if works OK again. You may want to try logging out & in and/or rebooting after making the changes.
iface lo inet loopback
There are no dumb questions, just dumb answers.