After using Cocktail (the appropriate version) on my G5 iMac running 10.4.11 and tweaking the network settings last night, I came in the AM after a cold boot to find myself unable to use ALL internet services. Safari gave me a helpful error, something along the lines of "POSIX error, no buffer available" or some-such.

Handily, apple/support/discussions had this nifty thread that explained how to fix it.

Delete the folder /Library/StartupItems/Cocktail.

The helpful discussion in discussion:

http://discussions.apple.com/thread.jspa?messageID=5865520�

I suggest the programmer either fix or idiot proof this setting area, and anyone who doesn't know precisely what they are doing leave it alone.