Bug#697501: AR9285: enabling or disabling Wi-Fi freezes the system

Additional information.
2.6.39~rc4-1~experimental.1 also hangs (rarely). Normal working version 2.6.38-5

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References:
- Bug#697501: Atheros AR9285: enabling or disabling Wi-Fi freezes the system
  - From: programmer11180@programist.ru
- Bug#697501: AR9285: enabling or disabling Wi-Fi freezes the system
  - From: Jonathan Nieder <jrnieder@gmail.com>
- Bug#697501: AR9285: enabling or disabling Wi-Fi freezes the system
  - From: "programmer11180@programist.ru" <programmer11180@programist.ru>
- Bug#697501: AR9285: enabling or disabling Wi-Fi freezes the system
  - From: Jonathan Nieder <jrnieder@gmail.com>
- Bug#697501: AR9285: enabling or disabling Wi-Fi freezes the system
  - From: "programmer11180@programist.ru" <programmer11180@programist.ru>
- Bug#697501: AR9285: enabling or disabling Wi-Fi freezes the system
  - From: Ben Hutchings <ben@decadent.org.uk>