Selective WiFi networks

My iPhone 5 will not connect to my WiFi networks but works on other WiFi networks... Currioisly it see's the network and gets both IP andress and Subnet Mask but no other data and no WiFi symbol / connection. Running airport utility it sees my Time machine and the internet connection as green and will even let me enter / configure it.

Now here is wear it gets strange...

It worked no problems for about 6 weeks then suddenly not working. There are 2 iPads, another iPhone 5 and a Macbook Air running on this network, all no problems

Stranger still

I have a second network (netgear running G) all other devices work on that as well but not my iPhone. The iPhone connects at work, when out and at my parents normally.

Now for proper strange...

I have replaced the iPhone 5 (from Apple store) for this exact issue 6 weeks ago, again the first phone worked fine for about 6 weeks

Ok this is the setup

Time Machine running WiFi G/N network running;
5 iOS devices
1 OS X
1 PC (I feel I should be honest)

Backup Netgear WiFI router running G network
All above if connected run no probs

Troubleshooting so far

Hard re-boot of all units
network deletion from iPhone and reconnection
WiFi on/off etc

Bizaar no?

Anyone?