I'm having this problem too.
I was using Philz touch recovery to restore my stock nandroid to see if the location issues I was having was device or CM11 specific. I got the /data message the OP posted, but did not think anything of it as I did not really care about any data as the device was virtually untouched from purchase.
I am not able to boot into fastboot or recovery. Adb does not see the device. When I boot it connected to my PC via usb I can see this for a short period before the window closes on it's own.
Device is Verizon branded
[UPDATE]A friend pointed out that if you use the stock "Close apps and reboot" option it is a slower boot. Once you select that hold power and volume down and you can get into fastboot. From there I was able to get into recovery and reflash CM11. Can not get my stock nandroid to work though.
"The world is indeed comic, but the joke is on mankind." H.P. Lovecraft 1890-1937