I was one of the idiots who tried to change to the EU region on a US system and killed my nav unit...dead. Lexus said there was no fix, I even called the 800 number.
There were several fixes posted here and on other sites but none worked for me.
What did work was sending it to a guy in Detroit called ToyoLexNavSpec. He fixed it like new for less than the cost of a new disc. You can find him on EBay selling nav systems (this was where I found him) or email at tahirmallick@hotmail.com . I'm getting nothing for posting this from him, I jut know that there are people out there who would like to get their system fixed.
I also think another guy who goes by egusman can fix them.