Strange Error in error.log possibly Internet-Sharing related

I recently got this error message repeating every 2 Seconds or so (date and hostname clipped):

+InternetSharing[524]: Internet Sharing shutting down+
+com.apple.launchd[1] (com.apple.InternetSharing[524]): Exited with exit code: 1+
+com.apple.launchd[1] (com.apple.InternetSharing): Throttling respawn: Will start in 10 seconds+

Internet-Sharing was disabled. After enabling and disabling InternetSharing. The error stopped. Only to be replaced by:

+natd[542]: failed to write packet back (No route to host)+
+natd[542]: failed to write packet back (Host is down)+

No IP-Adress is shown.

Occasionally I get:

+mDNSResponder[16]: setsockopt - IP MULTICASTIF error 169.254.98.218 -1 errno 49 (Can't assign requested address)+

Anyone any Clue what's wrong?

Message was edited by: shorshe