How does one re-set or edit the /system/build.prop, when changes kept it from booting up again? Rooted Optimus.
Try rebooting into recovery and connecting to the phone via ADB:
It should give a message like this:
List of devices attached 01234565ABCDEFG recovery
You can then copy the file off the phone:
adb pull /system/build.prop c:\build.prop
You can now edit it in any text editor (recommend Notepad++ because it will preserve the Unix style line endings,) and then copy it back to the phone:
adb push c:\build.prop /system/build.prop
If the issue was indeed within that file, the phone should boot now.
I was able to restore the factory firmware using the instructions here. Worked with no problem on Windows 7. :)
I guess this is why we should use custom-recovery like Clockworkmod?