What was the name? Maybe symbols or extended characters caused problems.

the name is 'Responsive Shiny'. When I changed it to 'asdf', I could save my new layout.

I think this is/was the reason for tihis:
all names of "storable" issues like files, pages, themes, layouts a.s.o. should not contain spaccse or special characters !
Only in pages names these will be exchanged with underscore or hyphen automatically , but not on files-names and here in layouts .

Um… but I can create layout with same name on my test site: http://test.scp-kr.net

0k, ;) - than this is a question for the developers…