Right-click on the Wireless Icon in your System Tray to display the Wireless Networks. If you mouse over your Router's SSID, a popup dialog will appear. The "Radio Type" will display the protocol of the connection.
If it is NOT "N", launch Device Manager, right-click on your Wireless Network Adapter device and choose "Properties" from the popup menu. Select the "Advanced" tab and confirm the "Wireless Connection Mode" is set to "Auto".
While you're in "Properties", go to the "Drivers" tab to see what Atheros driver version you're running. Uninstalling the driver, REBOOT, reinstalling the current (or most recent) driver for the device would be the next step.
G74SX-A1 - stock hardware - BIOS 202 - 2nd Monitor VISIO VF551XVT