What new mod(s) have you installed since having the problem?
I just remember reading about DarnUI not working alongside PDA or Readius on another mod page with someone having UI issues. I thought it may've been in Darn's thread under Known Issues, but no :shrug: I used to use the Readius and when I read that thought I wouldn't be able to use that character again.
Had the same problem, you're missing masters. Look at the description of the Merged Patch and the versions it requires of each mod and make sure you have the version it requires (or higher).