[asheshouse]

Most likely that you have duplicate or incomplete *.ini or *.properties files.
These are altered every time you add a new aircraft, object, ship etc.

If you have no idea what mod caused the problem I would suggest that you start with a reinstall of the UI, and then check that it works after the install of each mod.

If I am adding beta mods I always open the installer to see what files will be overwritten before starting and keep backups.