Nvu 1.0 (20050629) still works here, now Kompozer on the other hand is a slightly different story. Initially upon 1st attemp it appeared to try to start up, the main window flashed and it went away afterwards.
As Dave suggested I was guessing there is some sort of incompatibility between it and FF45.x that I'm running. I went to CLI and started the *cmd that my WPS objects points to, which is:
SET LIBPATHSTRICT=T
rem the following may only needed if another Mozilla based app is in LIBPATH
SET BEGINLIBPATH=G:\code\tools\kompozer
REM SET MOZILLA_HOME=<profile_path>
G:\code\tools\kompozer\kompozer.exe
...well, strangely enough that came up fine. So what I seem to have here is KompoZer 0.8b4pre (20100331).
Further on, as I attempted to re-start it again it still flashed and went away...however, re-starting the very next time made it come up just fine. So literally on my machine here, for whatever reason, I have a repeatable cycle of:
1) 1st start - main window flashes and app dies
2) 2nd start - full app comes up
3) 3rd start - back to 1st start behaviour
4) 4th start - back to 2nd start behaviour
LOL...go figure!