UI settings are from user's own computer, not server side or anything.
Cya.
Curse Client actually attempts to store some of that data server side (on Curse's server) and increases the chances of losing UI settings.
The best thing to do, as was suggested above, is to make sure once you are done configuring all your add-ons and characters and layouts is to close the client without crashing it.
If you crash right after you are done configuring you lose all your settings.
Just to make it clear.
1) Log in game, configure everything (LEAVE NOTHING BEHIND).
2) Find Hidden Runes of Magic folder in "My Documents".
3) Copy that folder and name the copy "Runes of Magic Back Up".
4) Make sure you avoid using add-ons that could possible corrupt your settings. (Older ones especially and a few add-ons also bloat up your UI settings, clearing them out help in loading time)