Have you tried the 'forget this network' option for Macca's (Aussie slang term for McD) in WiFi settings and re-scan it again and then tried to connect to it again?
Also check the WiFi Advanced settings to see if there are any there that may help., e.g. WiFi optimization etc
Not sure re your phone but when in WiFi area in Settings tap the right hand soft key below the screen to bring up more menu options, select Advanced. Alternatively there may be an icon on the screen (3 vertical dots perhaps) which brings up an options menu