corrupted OS, having trouble flashing

[jkweiner]

First, apologies if this has been solved somewhere on the forum, as I haven't been able to find it.

My rooted Verizon S4 became unstable a few weeks ago; random re-starts, bizarre battery draining, inability to re-start unless connected to a charger, etc.. I did a factory reset and the problems persisted. I installed Kies and downloaded the original stock ROM, but Kies was unable to connect to my device. After poking around online, I ran Odin and tried to flash the stock ROM that way. Here's how that went:

<ID:0/004> Added!!
<OSM> Enter CS for MD5..
<OSM> Check MD5.. Do not unplug the cable..
<OSM> Please wait..
<OSM> SCH-I545_MDK_562219_Stock_Restore.tar.md5 is valid.
<OSM> Checking MD5 finished Sucessfully..
<OSM> Leave CS..
<ID:0/004> Odin v.3 engine (ID:4)..
<ID:0/004> File analysis..
<ID:0/004> SetupConnection..
<ID:0/004> Initialzation..
<ID:0/004> Get PIT for mapping..
<ID:0/004> Firmware update start..
<ID:0/004> SingleDownload.
<ID:0/004> sbl1.mbn
<ID:0/004> NAND Write Start!!
<ID:0/004> sbl2.mbn
<ID:0/004> sbl3.mbn
<ID:0/004> rpm.mbn
<ID:0/004> aboot.mbn
<ID:0/004> FAIL! (Auth)
<ID:0/004>
<ID:0/004> Complete(Write) operation failed.
<OSM> All threads completed. (succeed 0 / failed 1)​

Now when I start the phone, I get the "Firmware upgrade encountered an issue. Please select recovery mode in Kies & try again." message. Only Kies won't connect to my phone so I have no idea how to proceed.

If anyone has any suggestions, please help! I'm sure I left out some pertinent details, so let me know what else I need to tell you...