Problem with Google Play Music on HTC One, just had system software update Android 4.4.2 Software 5.11.401.10 so may be related.
Can only stream music if "Stream via Wi-Fi only" setting is cleared. Phone is connected to WiFi and is using it to stream perfectly normally - streams quite happily with mobile data disabled and WiFi connected. as long as the flag in Settings is cleared.
Anyone else seen this or know how to fix it?