static IP not acting in Kubuntu 8.10 - cannot access internet

[ahmedmu]

I fresh-installed kubuntu 8.10 recently but although my ethernet device is detected, no network access is available and even after i tried to manually configure new wired connection with static IP addresses (which works fine with my kubuntu 8.04 installation) i dont have internet access.
From a suggestion by someone in the bugs report section i tried to edit network interfaces file manually (/etc/network/interfaces) kubuntu 8.10 prompts - cant overwrite/edit the file because it fails to create a backup of the file. I then backed up the file (etc/network/interfaces) manually and then tried to edit it (in text mode with kate) but it fails with the reply - cant overwrite the file with possible reason being no write access or no root access (which is wrong because i had root access with pw). i then tried to alter the properties ofthe file but the read/write option boxes are greyd out meaning not modifiable .
So, in effect i have twoissues -
a) why cant i configure network manager to accept static IP access the way that always worked for previous versions ( i have upgraded from 7.10 to 8.04 previuosly ) ? and
b) even as root with right pw why cant i edit config files manually ?