Default [Q] What does it mean when ODIN MODE boots up into "Downloading..."

I have a Tab 3 8.0 which I've done various installs with, and am trying to get back to stock.
But I can't, because when I enter recovery (power + down), ODIN MODE comes up with
Current Binary: Custom
Current Status: Custom

Downloading...
Do not turn off target !!

I've tried flashing stock firmware, other firmware, stock kernel etc.

I've read the process for going back to stock in the Tab 3 8.0 forum, but i think Odin (on PC) is failing because of the "Download..." state on the device.
(Also, when I try to run Kies it just continuously tries to connect to the device without success. The device will show up as media device in Win 7.)

Galaxy S3 L710 - The Collective --- 4.3.1
Galaxy Tab 3 8.0 T310 - CyanogenMod 10.2 --- 4.3.1