keep getting "there was a problem connecting with server" in El Capitan

Hi guys,

I've tried to sort out myself but so far no joy.... :-(

I'm running El Capitan on a MacBook and weeks ago I need to instal a specific program via CDROM and connected with my old Mac Mini (Tiger) via my WiFi using it as an external hard drive.

Everything worked well but afterward I keep getting this annoying message "There was a problem connecting with the server...."

So far checked:

1. the Mac Mini service is not listed in the login items

2. The Mac mini is no longer connected to my network

It seems like this message has something to do with my iCloud service, I've tried disconnecting and deleting, and fixed but as soon as i re-activated iCloud it started popping-up again.

Any suggestion?

Thanks

Sebastiano