YES (folder name: sony_dtv0FA10A01A0A1_00000100)...

As you can read above I made the update a chinese 4GB MBR FAT32 stick. Copied the above folder into its root, and attached it to the TV in power off. Pushed the connector to the mains, the TV was in out of order state. Then I pushed power+source together on TV tast, and then started to blinking Y-G led and the stick too, it started update immediately. If stick blinking continously Wait for long time. I think it restarted 2 times and finally started with baclight and normal working.
(I think the most important that the TV let in Y-G blinking state, the update will start if usb attached before...

A big thank you for all!
That was the problem: I copied only the file not the folder. And also a good news that, I reformatted my 4GB chinese led stick with RUFUS to MBR partition and USB update went down easily immediately, so doesn't need special low capacity stick for it.

PS: So far I have done many USB update, but almost all need to copy the (bin, pkg, etc.) file to root, not the folder. This is exception....

I have copied "00000100_07e8046a.bin" to the pendrive from "sony_tvupdate_2011_4027_eua_auth.zip". There is no change if I wait for 30-40sec. after G-Y blinking. Also tried to rename upgrade.loader.pkg
I will try to obtain a max. 1GB pendrive and try again.

I also confirmed my stick has MBR partition.

I ran into the same issue. I want to take KDL-32EX720 mainboard (works fine in original TV) into the KDL-40EX726. G and Y Leds blinks, but USB fw update not starting, only 1 sec communication visible on status led. I use an old 4GB Kingstone pendrive, which worked well in any TV so far. Tried EUA and AAA sw., original .bin and upgrage_loader.pkg, etc.