This issue may be related to the type of encryption. Windows* connects the best using WPA2/AES security. We recommend that you first contact HP* and see if they have any updates that myght help you resolve the issue: HP Customer Support | HP® Customer Support
As a second option, you can use our latest drivers version (18.21.0) found in our Download Center: Downloads for Intel® Dual Band Wireless-AC 7260 make sure to chose the one that is right for your system architecture (32 or 64 bit) and version such as Window® 7, Window® 8.1 and Window®10
I have had a HP engineer on-site because they are concerned that we have so many with the same issue !!!
They told use to try (Intel) here
I currently have driver version 126.96.36.199 - dated 29/9/2014 - installed, but from your link I can only see 17.1.1531.1764 - dated 22/9/2015 - which seems very strange - these PCs must use Win. 7 64bit Enterprise.
How could 17.1.1531.1764 be newer than 188.8.131.52 ???
This is exactly why I asked the questions I did in the OP !!!
Remember I already have 80% of these PCs working fine & I'm wasting a lot of time on this now
When I right click "Intel(R) Dual Band Wireless-AC 7260" in device manager & click Drive Tab the details are
Provider : Intel
Date : 29/09/2014
This is the same for working & non-working PC !!!
So I cant see how this has anything to do with the driver as I'm using WDS/ MDT to image & I have used it to re-image the PCs
Thank you for your time, after researching on this particular issue we recommend that your contact your nearest Intel Contact Center and engage one of our technicians for live assistance.
Click on this link to find the best way to contact our technicians: Contact Support - Should you have any further questions or doubts, please do not hesitate to contact us.