Thank you for any suggestions.
I have the EXACT same problem and need to restart the computer when it happens. My model is the Inspiron 640m, purchase in July 2006.
Try this little tweak and see what happens.
Go to device manager(right click my computer, left click properties, left click hardware, left click device manager). Click on Network and then right click on your wireless adapter, left click properties, power management. Uncheck the box, allow computer to turn off this device to save power.
Original poster, If you have solved your problem, can you please mark the correct thread(s) with your solution. Thanks
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I have the same problem and can verify that this doesn't always work. I don't know what it is but i think it might be a motherboard problem because I have replaced the wireless card in an attempt to fix this along with a reformat and installed all the drivers.