Hello.
Can you provide more information about your Wireless Network setup? Question list below will better help us understand the setup and possible cause for this.
1. Manufacture and Model of Router
2. Is the network protected by WEP, WPA, WPA 2 Personal Security
3. Are you using Mac Address Filtering
4. Are you using Static IP address or DHCP address
*Things to try on iPhone and Quick tips
-Shut down the Emac and the iPhone. emac can be shut down via apple logo. iPhone can be shut down via holding down the sleep/wake button and sliding to power off.
-Turn emac on, check and see if it can connect
-Turn iPhone on and check and see if it can connect
*Turn of WiFi on both emac and iPhone
-iPhone - Settings - WiFi - Off, wait 30 seconds turn back on and connect to WiFi
-emac - Click on Airport icon - Turn Airport Off, wait 30 seconds, turn back on
iPod touch and iPhone: Tips when using Wi-Fi
http://support.apple.com/kb/TS1398
Unable to use Wi-Fi with iPhone or iPod touch because there's no Wi-Fi address listed for the device
http://support.apple.com/kb/TS1559