Flash went smoothly to TWN. Only one goddam EN voice available in the firmware pack though and it's the twangy Yank Jill. I remember now why i flashed to SG/MY, much better choice of voices including the lovely dulcet Aussie Karen and another one of my favourites, the silky voiced Pom Daniel. Did you remove or rename your US voices and replace with the Voice folder contained in the extracted TWN exe? If not maybe your unit was part-bricked by having incompatible voices onboard and that's why it stuck on the Locale screen. I assume you slid the power button from lock back to centre position after you disconnected from PC.

If you're determined to stick with TWN i can modify the rgn file so you have a wider choice of EN voices, including Jack. Or you could flash to SG/MY instead and use their voices [included are Jill, Karen and Daniel without modification]. I really didn't want to turn this into a tutorial, but it seems to be happening ... kinda the death of a 1000 cuts tho, lol!