I attempted to install the OTA update for 4.4.2, but received an error message that the installation failed. When my phone rebooted it was unable to connect to the cell network and was extremely sluggish. I own an iMac and the S4 is no longer recognized by Kies or Android File Transfer.
I attempted turning off the phone and removing the battery and Sim, to no avail. I also attempted to access the recovery tools, but the phone will no longer boot to recovery. I tried a factory reset, but I do no recall ever setting the security PIN it seems to require.