What is this? Pop up in Safari with red warning sign saying something about an ip address?

[kj4btkljv]

It is possible that another machine on your network has the same IP address, and when you go to open Safari, your machine "checks in" with the router. When it finds the duplicate, the OS pops up an error window. You are probably just in Safari, and therefore think it's coming from the browser, instead of the operating system.

Have any other machines on your network, or are you all alone?

Jeff