Same issue. I ended up buying 4 replacement wifi modules to get the wifi working. The cards I bought also were tested and had 100% functionality. What occurs to me now, is that the macbook pro A1278 does not have plug and play hardware functionality. In other words, if you're swapping or adding new hardware.. it might not show up instantly as new hardware on the osx. What could work is a reinstall of osx after you've added the new hardware. Sounds bizzar, but worth a shot.
If you want to go with another solution for wifi without having a huge dongle sticking out of your usb port, you should try the Eye-Fi SD cards. Basically an SD card that also has wifi on it. It'll pop into your SD slot and be hidden from view.
Hope this helps,
good luck