Boot screen hangs even after factory reset

My Droid Razr XT910 was constantly booting and after a forced reboot still hangs here. As a next step I wiped out the data via the boot menu, i.e. a factory reset. But the phone still hangs with the boot logo. My phone is stock, not rooted. I let it constantly load over night, until the battery finished. Two days ago I tried the factory reset, but it didn't result in showing the home screen. I did several factory resets just to check. Is there any way to let the phone boot again? Thanks for your help.