I have a HP Pavilion dm4 that initially came with Windows 7. I upgraded to Windows 8 and then replaced that with Ubuntu 12.10. The WiFi worked fine until I installed the software upgrades right after installing the os. There is a hardware switch for WiFi and Bluetooth and it is on.
rfkill list all results:
2: hp-bluetooth: Bluetooth Soft blocked: no Hard blocked: no 3: hp-wifi: Wireless LAN Soft blocked: no Hard blocked: no 4: hci0: Bluetooth Soft blocked: no Hard blocked: no
In the Network settings, I only see Wired and Network Proxy, no wireless. I am currently connected to a wired network to resolve this issue.