This is an odd one - wireless devices suddenly unable to connect

[#1]

Is it conceivable that it is one of your wireless devices causing the problem? If the issue returns is it worth turning them all off and then restarting them one every 20 minutes or so?

[#2]

I've had this problem for the last month.  Plusnet solution is to tell me to get a new router from them - they're cheaper at Amazon.  Then they offered me one for free if I sign up for a 12 month contract ... but I'm reluctant to do this as I'm not sure the new free router will solve the problem and I don't want to be stuck for 12 months with this problem.  I might be better just trying another IPS. 
The advice you've got on here is better than you'll get from Plusnet from the experience I had.  They say it has to be the router if the cable works so basically it isn't their problem. 
Anyway, I'm watching this thread with interest!
Good luck

[#3]

It's been a few days now, and still everything is running fine.
I'm wondering whether the comment made by NedLudd could actually be the case. I have been reseraching this in more detail and found on other forums (fora) the almost exact same problem had been encountered by others.In all cases, it turned out to be a clash with someone elses router gateway address.  There is even a video on YouTube explaining how to effectively 'Jam' wireless users out at hotspots by locating the IP gateway address of the hub and changing your phone gateway IP address to the same.  This would probably explain why putting the Home Hub 3 router resulted in the same problem as it uses the same gateway address.
I don't thing anyone nearby is doining this deliberately. I have since spoken to my neighbour and brought this issue up in conversation. He said that he has lots of gaming equipment and also a wireless link from his phone to his tele (SECLINK or similar). He said he wasn't sure if he was using the SECLINK when I had my problem but he does use it occasionally, so we will set up a test when he returns from business and see if we can recreate it.  If it's not him, then maybe someone else is doing the same.
If it does happen again and we determine that it isn't teh SECLINK thing, the I'll take NedLudd's advice and change my gateway adress and try again.
Thanks for all your comments so far.
By the way, support just said I should bear it in mind and close the problem off in two weeks if the problem doesn't happen again in that time.

[#4]

If the problem turns out to be some sort of IP address clash, it would have to be a device within your wifi network. The IP addresses are part of the encrypted data transmitted over the wifi, they aren't visible without the wifi security key.

[#5]

Thanks ejs.  I have ruled that out now as all the devices that were there before the apparent clash were there and active when the problem happened, and are there and active now it's all working again. Absolutely no changes have been made to any of the cofiguration vakues for any of these devices  To further qualify this, I ran the single 'one unit at a time' test, and the problem didn't happen.
I still heavily suspect that the gateway adress was being compromised somehow.  It will be interesting to see if it can be recreated when I ask next door to turn his television link back on again.  The only head scratcher there is that he claims to have used this system many times in the past year, so I'm sure I would have had this problem before if that is in the frame.
We'll see.  If it isn't him, then I'll have to run some more specific tracing.

[#6]

Quote

I still heavily suspect that the gateway adress was being compromised somehow.

Your gateway IP address 192.168.1.254 is on a private network, ie what is termed as private IP address space. These IP addresses are not routable because they are not delegated to any particular host(s), their intended purpose is that they be used internally on private Local Area Networks (LAN). Organisations use them internally without any of these addresses conflicting with the next door organisation, using the same private addresses on their LANs.
The only way any of your private IP address can be used by a third party would be if they had your wireless SSID and security ID. Even then they would not be able to use any of the IP addresses that are already in use.

[#7]

Just by way of an update, we have now positively identified the reason for this.  It is solidly recreateable. There is no longer any doubt as to the root cause of this issue.
My immediate neighbour has Samsung 'smart' TV with a wifi link. Whenever he activiates it's wifi to perform a film download, our wifi, although still visible on the wifi list, is completely locked out.   When he stops the download and de-activates the 'SECLINK' wifi, everything returns to normal.  We ran this test three or four times and recreated it every time.
Thanks to my neighbour for agreeing to test this out with me.  He said that if he needs to do a download he speak to us first, even though this is not his problem.   We will simply used a wired connection during this time should we need to use the internet at the time.
Found this on a Samsung discussion forum that backs this up:

"While playing around to improve the WiFi network reception of my Samsung LED TV, I enabled SWL.

It didn’t do much on the WiFi reception, but I found out that after enabling SWL, other devices could hardly find my regular access point any more.

Somehow, a very strong access point appeared pushing away all access points. The new access point had an SSID like SEC_LinkShare_######.

Though this wasn’t mentioned in the PDF  manual of my TV, a quick search on SEC_LinkShare+SSID indicated in the direction of Samsung devices.

So, when you enable SWL on your TV:
1.your TV will become a local secured access point
2.the SWL access point will be called SEC_LinkShare_###### (with 6 digits at the end)
3.you cannot influence the WiFi channel used by the SWL access point
4.there is no information on the password to connect to the SWL access point
5.the SWL access point will potentially have a higher signal than access points further away (effectively blocking them)

Conclusion: Unless you have other Samsung devices that need the SWL, don’t activate it on your TV."
Hopefully this will be the end of it, and may be of use to others that had erratic wifi reception at certain times.

[#8]

This http://wiert.me/2011/07/04/sec_linkshare-ssid-is-from-your-samsung-tv-swl-samsung-wireless-link/ looks like the same problem. It claims that it doesn't need SWL active UNLESS you need to connect devices to the TV.

Quote

So, when you enable SWL on your TV:    your TV will become a local secured access point    the SWL access point will be called SEC_LinkShare_###### (with 6 digits at the end)    you cannot influence the WiFi channel used by the SWL access point    there is no information on the password to connect to the SWL access point    the SWL access point will potentially have a higher signal than access points further away (effectively blocking them) Conclusion: Unless you have other Samsung devices that need the SWL, don’t activate it on your TV.

The same problem here http://community.virginmedia.com/t5/Up-to-30Mb-Setup-Equipment/TV-interfering-with-SuperHub-wireless.... Also explains how SWL can be accidentally on.

[#9]

Please see my blog post about SEC_Linkshgare here: http://jumpingspider.co.uk/samsung-wireless-link-or-wtf-is-sec_linkshare
This is one massive security hole in your network if you allow your Samsung TV to use SWL.