Just stumbled across an ugly bug in Concrete5 (5.4.0.5). I tried to install my newly created theme called bfd. The install button did not do anything when pushed. The theme would not be installed. After a good while I found out that C5 did not like the name that was three letters long.
After renaming the theme to befde the theme could be installed without any further problems. Nice one – if you know it.