Airport turns off and won't turn on again

Hello everyone,

I'm having problems with the Wi-Fi on my 15" MacBook Pro (from 2011) running Mountain Lion. Since last week, the wifi only works for 5-10 minutes after booting the computer. After that time, Airport suddenly turns off, and can't be turned on again (I've tried to turn it on both using the drop-down menu at the top of the screen and by going into System Preferences). The only way to turn it back on is to reboot the computer, but then the story repeats itself and the wifi drops after 5-10 minutes.

I have now experienced this at a number of different network locations, and in all cases the other computers on the network have had no problems at all. This problem started suddenly last week and is not happening after a hardware or software update.

I have tried resetting the PRAM and the SMC, but it hasn't helped. I have also tried installing Mountain Lion again using the Recovery Partition, but it didn't help either. I have also tried renaming my network location and changing the value of the wifi MTU as some have suggested for similar problems, but it doesn't help.

I have searched for other discussion threads on this, but have not found anything on exactly the same problem, and have not found any solutions that help. Would you think this is a software or a hardware issue? Does anyone have an idea how to solve this issue?

Best regards,

Dadi