Ok, first I would like to say thank you very much Khun Aekhong, your help was the only thing that helped me fix this issue. I still can not find any information about this on the internet, yet you were able to help me so quickly. Again, thank you.

I have resolved the problem. I tried many times to use the updater with several different rgn files, without success. I even tried to make a cure firmware and that didn't work. Finally I was able to update the device and now it boots correctly with the latest firmware from US.

Now, please can you tell me what is the best firmware to update it to use the newest Thai maps with JV and 3D and Lane Assist? Is it possible to update this unit (3790T US) to the Thai firmware? Or will the SG/MY or CH firmware allow this? Your opinion would mean alot to me.