Do you mean that you have used the Wireless Security feature of OneCare to secure your wireless network, but now your iPhone can't connect to your router?
If so, the following from Instant Help should cover it.
To add a device to a newly secured wireless network, follow the instructions in the manufacturer's manual for the device. If you need more help, contact the manufacturer of the device.
Note
You must enter the SSID (Service Set Identifier, also known as the network name. A unique name entered to access a WiFi network that enables communication between network users and the access point.) and network key to add a device.
To add a computer to a wireless network if you used the Add a PC wizard in Windows Live OneCare:
- On the computer that you used to help secure the wireless network, click Change Settings.
- On Firewall tab, click Advanced settings.
- On the Network connections tab, click your wireless network, and then click Details.
- The SSID and network key appear in the Security Information area.
Note
If you added a computer or a device to the network manually, read the instructions in the manufacturer's manual, or contact the manufacturer of the router for information about how to obtain the network name and network key.
-steve