are these IPs always the same?
Don't know exactly.. cause the IP won't be logged. Today they are the same (but this can change via dynamic IPs).
did you try trace/"whois" them?
Yes, the provider is (both) bluewin.ch: "BLUEWIN-3PLAY-NET"
Some ISP use proxies (AOL) and each client's request can come from different IP...
This could be the problem. I know the user, but he doesn't know anything about it. Maybe Bluewin offers 2 IPs its user.