Mac OSX Mavericks.
Use Bridge and PS all day, occasionally use lightroom to modify EXIF details. As I tried today.
First I launched it and it just disappeared... mmm thats odd..
so after a few more tries I deleted it from the application folder, reinstalled from the Creative Cloud app, and same thing.
so I deleted the preferences file and all that and tried again, still nothing. LR flashes up for a second and then its gone.
So I signed out of CC and deleted the LR app, signed in and reinstalled. now it works. WTF... weird licensing issue I guess..