First of all, Chris, sorry for the delayed reply.
If you have no information regarding wireless security in the advanced settings for OneCare, then wireless security from OneCare was not configured, most likely because your router is not on the supported list.
So, although the problem began with the installation of OneCare, it is likely asking you for the key that was configured on the router - you will need to supply that to connect. Why it was lost I don't know, but suspect that it may be due to the fact that the firewall component made changes to the network connections.
If you no longer recall the key used on your wireless router, you will need to reconfigure your router manually as well as any devices that also connect to the router wirelessly.
-steve