Macbook Air and Mac Mini can't connect to each other

[mjt57]

I have a Macbook Air and a Mac Mini, both bought earlier this year. Each is running Mavericks.

I can't seem to access either machine's drive from the other. Each sees the other in Finder under "shared" but when I try to log in to it I get "connection failed".

The MBA is on WIFI whilst the Mini is connected to the LAN via ethernet.

Any suggestions?

Thanks