Airport does not always detect O2 wireless box

On my macbook, airport usually detects the o2 wireless box and connects fine (4 bars etc). However, every now and then airport can't find the connection, even though the wired network works fine.

The most confusing part is that, when connected and not connected, the wireless light is on red on the o2 box. Is this affecting the macbook, or is it something else?

Thanks for any help,
David

Never mind, I enabled some type of encryption within the config page and it sorted it out.

thanks for the helpful responses.