I had Google Play issues, error 403, 920, 923, so I tried a fullwipe which I had used without any problems on my Desire HD. But I've encountered big issues on my Nexus 5...
It's stuck in bootloop, but I can get it to fastboot and recovery. I can't get it to mount USB-OTG (think that's wiped)
It won't show up in ADB (I am in fastboot), worked BEOFORE I flashed Custom Recovery (it broke after I installed), and did not work before I got all the errors. I can sideload CM11, but flashing wont help.
I'll try to get adb to work in fastboot, reinstalling drivers etc....
EDIT: Here is the zip i flashed do a full wipe. So you scriptheads know what messed things up