Cannot connect to network

Try use WPA2-PSK only as your security, does that work?

I like to keep a track of problem like this here:- http://www.unofficialguidetolive.co.uk/faqs/166-wireless-gaming-official-wireless-adapter-incompatibility-list

So at the moment when set to B+G+N with or without security it doesn't connect, but when set to B+G without security it does connect

And if its not an SSID issue try changing your wireless settings from B+G+N to B+G and see if it can connect with no security using Wireless G

Also turn off that wireless mac address filter for now

So you are using NetCommLEM_86_N_A11_21290_312140_2M16_ras.zip from here?
www.netcomm.com.au/.../nb14wn

If so I'm afraid it sounds like a compatibility issue to me. Your SSID have you left it on the default "Netcomm Wireless" or is it something else?

The Xbox doesn't like spaces in a n SSID so ensure there are no spaces in yours, it needs to be a single word only

Sorry for posting a second time.

I also turned off the WPA2 security and it didn't work either.

Wasn't sure how to change the broadcasting speed either.. so it might not be an option.

And I upgraded the firmware a couple days ago, which I thought might have been the source of the problem however I restored a backup and it still wont work.

Silly question but you have been through the set up process to connect your Xbox to the network?

Checked that the Xbox is on the allowed list in your router settings maybe and not blocked from accessing the network in any way.