I created a temporary network using my laptop (Windows 7), but my mobile phone (Symbian S60) could not connect to it (the status of the network is always waiting), either in public mode or with WEP authentication.
Another laptop can connect to this network and access the Internet through the shared Internet connection, and my mobile phone can connect to a public WiFi access point normally.
I chose "Ad-hoc" as the WLAN network mode in my phone's control panel, and other settings (IP addresses, security settings, etc) seemed to be correct.