Airport Express Problem

Hi
I've just managed to set up my Airport Express but having a problem where it mainly drops out for a couple of secs every minute or so. I have it near my Mac so no distance issues and also have it connected on a Windows computer with exactly the same drop out issue.I only want to use it for streaming Airtunes, my main router is an O2 wireless box.If anybody has had the same problem and managed to fix it i would be very grateful if they could point me in the right direction of fixing it...........Thanks