I'm having the same issue. Headed to the store location for my third replacement. You get any answers to this issue ?

 

Man, this is not the news I wanted to read about. I just got my first replacement phone back today. It actually quit working beside the LED lights lighting up twenty minutes after I turned it on. I took the battery out and put it back in and it works.....for now. I am not looking forward to more replacements. If I hear anything fixes about this, I'll be sure to post them on here. Good luck.

 

Hello..first post here. I've had the XT720 for a few months now and have also had this issue. Everytime I've had it, it's been related to the SD card I installed. The phone comes with a Class 2 Micro-SDHC card and I replaced mine with a Class 10 for higher transfer speeds, but the phone did not like it and was doing this LED-only-on thing. Once I replaced the SD card again with a high-quality Class 6, the problem went away and hasn't come back since. No real technical explanation I found, more trial and error. Hope this helps.