I'm currently working the same problem on a LS670, with a logo to black screen brick.
I've been having the same luck so far. Trying all of the same programs, all with about the same result.
I thought I was getting somewhere for a minute when I saw something "new" on the phone screen, (caution downloading sign)
This was cool for a second until I saw that I still hadn't really gotten anywhere.
The biggest problem seems to really be that there is no way to "turn on" the USB debugging (or whatever they call it) so that the phone can "connect," or "accept," any of the software updates or flash programs.
The LG support tool seems to at least have some promise, but then again, I haven't found a KDZ yet that will successfully even make it through the loading procedure. (I think all I need is a good KDZ that will work right.)
I've already been out here for a while on this, and unfortunately, I have a feeling I'll be out here working on it for even a while longer. So if you hear of anything, please don't hesitate to message me and let me know. I'll do the same.
Good luck,
Policetac