I tried your tipps, but it did not work. Still the white point on the lower edge for one second. Fully charged battery, everything removed, fresh formatted card,....
And there was no moisture....
I phoned with the Canon support (2 min before closing), and the employee told me to send it to the German Canon service departement. He thinks the main processor is broken - maybe as an result of the fw-upgrade (then there will be NO warranty).
If you still have the Firmware which you downloaded on a CF, send it with the camera along with the explanation. The processor is unlikely to be broken. I'm no expert, but it sounds more like corruption in the firmware - and now, when the camera powers up, loading the firmware, it's not loading fully and it never gets to start. I've never heard of a firmware upgrade that breaks a processor, nor a camera failing right after an upgrade.
As mentioned, I would let them fix the camera first, and then suggest that you followed Canon's process for upgrading the firmware and therefore any fix should be gratis. I'd definitely appeal to their good customer service, before arguing warranty.
If you concur with others, then don't even mention the firmware upgrade. Just state it stopped working and go for warranty.
Best of luck.