This is a weird one. When double-clicking (or otherwise launching) a file associated with LibreOffice, the program launch freezes until I move the mouse or press any key. "LibreOffice" and "File" toolbar menus do become visible, but the file or application window doesn't load. I can wait a full minute. If I move the mouse (trackpad) or press any key (shift), the app launches and the file gets loaded in under 4 seconds total. Tested with .odt, .ods, .xls, .xlsx. LibreOffice 5.0.3.2 on OSX 10.11.1 El Capitan, MacBook Pro mid 2010.
try resetting the user profile and tell if it fix things https://wiki.documentfoundation.org/UserProfile
Renaming the user profile directory and rebooting did not help. I did see a new user profile folder being created, but the issue remains.
*** This bug has been marked as a duplicate of bug 77444 ***