Hi all, just thought I'd join up and post a solution, not a problem, because I found it the devil's own job to track down a solution on the internet, and therefore I'm guessing other folk may be struggling.
(If this is old news, then apologies in advance.)
If you have Intel Pro Set internal wireless card, most likely on a laptop, and are experiencing difficulties accessing your network from the laptop (such as your router not being 'visible' on the list of available networks, or getting the response 'Cannot connect to <insert name of router here>'), then as I have found you may need to disable the power management of the Intel Proset.
Apparently Proset uses 'Power Save Polling', which my Belkin Pre N and lots of other routers can't handle.
If you go into Settings and look for the Power Management one, move the slider to the right, for highest performance and minimal battery saving.
Once I did this I was free of the connection problems that had plagued me.
Despite the solution being on the Proset end, Intel blame the various router manufacturers:
http://www.intel.com/support/wireles.../cs-006205.htm
Anyway, like I say, there may be some other poor soul struggling like me, hearing about all the problems with <Insert brand here> routers and assuming that's where the fault lies.
Looks like a great forum, glad I stumbled upon it as I was looking for answers!