It's the same, so perhaps there is more to this than just the number of characters

Just made 26 toons on the leviathan (that's my limit) and didn't experience the freeze. Logged back to Star Forge (with 29 toons) and... freeze, as expected.

After turning the internet off and on I managed to get to the server selection screen upon launch, and I was able to log to every server, except Star Forge (I have 29 toon there), where I got the freezing loading screen again. Editing settings file did nothing. Also pref here, if that's of any use.