I uninstalled the 6.3.1 version, leaving only version 5.5.4 installed, reinstalled version 6.3.1 and restarted SqlNav. It again asked me whether to take over the 6.2.1 settings, which I confirmed. The program was present as a process, did not show a UI, but consumed 100% CPU of one core. I waited about 15 minutes, and as it was lunchtime, I left it running in “zombie-mode”. After lunch, to my surprise, SqlNav had started up!
Maybe it took a long time to import the settings? I’m running SqlNav on a P4 3.2GHz (hyperthreaded to provide 2 pseudo-cores) which is a bit - ahem - dated, but it’s by no means a slouch…
Anyway, since then, SqlNav starts up smoothly.
If you need anything (settings file?) please let me know.