Wi-fi acting strangely on emachines E525 laptops

The project that I am volunteering at has several Emachines E525 laptops that are intermittently having strange problems with their wi-fi connections. The nature of the problem is that the laptops don't see the wi-fi network that they are supposed to be using at all sometimes despite there being desktop machines and other devices on the wi-fi without problems and the laptops being able to see other networks. The problem comes and goes without apparent cause but when it does occur it effects all the laptops and lasts for periods of several hours at a time.

The laptops are identical Emachines E525s running Windows 7 Home Premium (which are regularly updated) and have Broadcom 802.11g wi-fi adaptors (according to the device manager anyway). The router is a BT Business Hub model number BT 2700 HGV.

Any help that you are able to provide would be greatly appreciated as the issue is ongoing and are very annoying.

but when it does occur it effects all the laptops and lasts for periods of several hours at a time

But only the Emachines laptops - how many - and NONE of the other devices connected to the wifi - the other devices are in the same room ? anything else common about the laptops and NOT about the other devices, like powersupply, room, etc - have you installed any software on these machines that are not on the others - what other laptops do you have , that work OK?

do they work OK any where else ?

it could be a faulty batch - did you buy them all at the same time

can we see an xirrus screen shot from one of the machines

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Run Xirrus Wi-Fi Inspector Download and install
If you cannot access the internet with this PC, then you will need to copy the program across to the faulty PC

http://www.xirrus.com/library/wifitools.php
Direct link to the program is here http://www.xirrus.com/library/wifi_download_redirect.php
Then run and install the program
if you get an error - You need NET Framework installed for the WiFi Inspector to function.

Run the program

post a screen shot of the program running - if there are a lot of networks showing can you click on "networks" top lefthand area - so we can see all the network information, and also post which network "Adapter Name" (1st column) is yours on the list

To post a screen shot of the active window, hold the Alt key and press the PrtScn key. Open the Windows PAINT application and Paste the screen shot. You can then use PAINT to trim to suit, and save it as a JPG format file.
To upload it to the forum, ohttp://www.bleepingcomputer.com/forums/topic14738.html
Note:
For a reliable (or robust as the Xirrus user guide says) wireless connection you need a signal of about -70 dBm or better.
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