[Q] Flashing 4.3 breaks download mode

I recently updated my I9300 to 4.3. The file I used to flash was obtained from sammobile.com:
TEL-I9300TDUUGNC1-20140418172117

I updated using Odin and all appears to have gone well. The phone is working and reports the correct version, expected baseband etc.

However, since I flashed, I am unable to get Odin to recognize the phone in download any more. The PC does not acknowledge the device was plugged in and no COM boxes light up. In short, the device seems to have the USB port disabled when in download mode now. Odin no longer seems to recognize the device.

Does anyone know why flashing 4.3 might result in Odin no longer recognizing the device?

To avoid clarifying questions:
- I'm using a Samsung original cable. It's the same one I used to flash the device to 4.3 with.
- I've tested this cable with another device, a GS4, which shows up just fine in download mode.
- I've installed the latest Kies.
- I've tried Odin3 v1.85 and v3.07
- I've tried looking at the PC and phone with a stern expression.

dxppxd said:

If all else fails, mobile odin is your friend, free version in android apps section.

Click to expand...

Click to collapse

Mobile Odin requires a rooted phone, and I don't know any method of rooting a phone without Odin. Are there any methods that allow me to root a phone without first flashing something with the USB cable? Are there any apps that can do it? Perhaps using an update.zip with the stock recovery?

To answer above questions:
- I've tried on another PC
- Can't be PC, because this PC can flash other devices via Odin just fine. This is the only device that is playing up.