Strange WLAN adapter behaviour; sometimes not detected

Question

I just got myself a brand new Toshiba Satellite L670-187 17,3" notebook. On first boot it worked fine and I could just connect to my wireless network immediately. However, when the notebook has been turned off for several hours, my WLAN adapter suddenly is no longer detected (nor is it visible in Device Management). Only my LAN adapter is detected and operational.

When I click "Detect new hardware" in Device Management, it detects the WLAN adapter but it won't connect to any wireless networks, instead it just displays the wireless signal bars with a red X in my systray. If I reboot, the wireless network is automatically detected and connected to.

When I power of the laptop and reboot after a few hours, suddenly the WLAN adapter has gone missing again. I turned off the option that Windows is allowed to power off the device to save power, have reinstalled Windows, reinstalled all drivers and tried all available drivers for the WLAN adapter I could find. As far as I know, it works fine under Ubuntu so I figure it's a Windows issue. Furthermore, the issue persists when using a not-OEM Windows disk to reinstall.

The network switch is turned to ON and FN + F8 doesn't do anything.

Below are the specs:

CPU:  
Type : Intel® Core™ i3-350M Processor  
Speed : 2.26 GHz  
Front Side Bus : 1.066 MHz  
3rd level cache : 3 MB  

Memory:  
Size : 4,096 (2,048 + 2,048) MB
Max expansion : 8,192 MB
Technology : DDR3 RAM (1,066 MHz)  

OS:  
Genuine Windows® 7 Home Premium 64-bit (pre-installed, Toshiba-HDD recovery)

Wireless network adapter:  
Realtek RTL8191SE Wireless LAN 802.11n PCI-E NIC 802.11b/g/n

Any ideas anyone?

UPDATE

If I update the driver automatically with Windows, the adapter is not detected anymore at all until I reinstall the original driver. I have already performed a BIOS update without success.

Answer 1

Three requests for information:

1. Are you using the Realtek driver from 05/20/10 ?
2. If you try an external usb wireless NIC, do you have the same problem?
3. I cannot manage to find your exact notebook model on Toshiba Support site. Could you please supply a link.

Answer 2

If you let it sit for a long time, it might be cooling and contracting. After its been booted up for a few, it might expand just enough to make the connection. Have you cracked open the computer, and reseated the wireless card? Its often sitting in a socket, just like RAM but smaller. You might want to re-seat the chip.

Also, stretching here, but do you have to reset the time when you leave it off for a long time? it might have a bad CMOS battery.