Are you talking about switch off wireless security ?

Well I wasn't but since then I have switched off the wireless security and I can now connect all four devices.
Obviously something wrong with the way I setup the security but I have no idea what.

This is my proposition how to configure router - LINK. Probably you have to switch off an automatic configuration on router and make drivers update.

So far every time I turn on wireless security I lose some of my connections.
I shall just keep trying.

You can use my tutorial from earlier post.

Whenever I activate the security, I lose the connection to my Vista pc so, for the time being, I shall run without security as I now have to concentrate
on finding a media server which will work with my Philips smart tv.
I guess I shall return with other questions later.
Thank you very much for all your assistance which is certainly appreciated.
Regards