Hi there I have been having some major headaches with wifi dongles on my macbook pro. Background: I have a very old MBP. About 18 months ago the airport card more or less gave up. I bought usb wifi dongle about 9 months ago and for a while it worked fine, albeit with an ugly utility. Then about 3 months ago the dongle gave up, or so I thought. The utility acted as though no dongle was connected, and I returned the dongle to the supplier, who refunded me. A month ago I bought an ASUS USB-N13, which claims to have mac support. With the software that came with the dongle, the result was the same - the wireless utility said "no device" with the dongle connected. Then I tried more recent drivers from the ASUS site and got a marginally improved result - the dongle showed up and did a scan of the signals in the area. But any time I attempted to connect to a network the utility crashed. I tried a few third party apps I read about but nothing worked. I tried ASUS support, who were utterly useless - they sent me the windows drivers, sent me to speak to the supplier, and eventually just said they can't do any more than that. (I'd advise against ASUS for mac users based on this experience). Today I tried to uninstall and reinstall the driver and utility but on both reinstalls I got this error: "System extension cannot be used. The system extension "/System/Library/Extensions/RT2870USBWirelessDriver.kext" was installed improperly and cannot be used. Please try reinstalling it, or contact the product's vendor for an update." This is beyond my level of technical competency - I don't know anything about kext, and the supplier and manufacturer say they cannot help. Although the installer completed and said the installation was complete, currently nothing happens when I plug in the dongle and it does not even light up on its LED. I don't know what to do but I desperately need a wireless connection. Can anyone advise? thanks so much.