Macbook Pro says no airport card is installed. Any solutions?

This sort of problem has been posted before but I've yet to have any success with solving it.

I've recently acquired a MacBook Pro (a 2009 model- MC118B/A) and since I got it, it's had a less than stable relationship with the internal airport card. Most of the time, it claims there isn't one installed!

I've tried booting up while powered from the mains, I've tried installing software updates (it's all up to date) and I even tried to clear the P-RAM (although I don't know if I got the keyboard mason-handshake correct because it didn't seem to do anything!). Is it a dodgy airport card or are there a few other things I could try?

Cheers