When I first got my AirPort Express I was having nothing but dropouts, trying to find a solution through Apple and forums, I found nothing that worked for me.
So if nothing Apple says or reading forums doesn't seem to work, try something as simple as doing what I did. I went into my networking settings for my wireless router and changed the channel on the router.
Mine was set to 'auto' and I changed it to '8'. I've had nothing but seamless and perfect streaming of my music for about 9 hours straight. It's ridiculous how such a simple change to a setting can do.
I changed it at noon and wanted to test it to see if it worked, I'm still listening to music without any interruptions or dropouts as I type this response.
I hope my solution works to any and all who try it, best of luck to you.