Can't stream music from iPhone to airport express when connected to internet

I have an issue with my airport express. When the unit is used solely for streaming music from my IPhone to connected stereo speakers without an Ethernet cable attached it works fine. When I attach an Ethernet cable to the airport express and connect to the Internet on my iPhone, the airport express will no longer stream music from the iPhone. This is a recent problem, previously I was able to access the Internet on my iPhone from the airport express, whilst simultaneously streaming music from the iPhone back to the airport express.