HI, i have the same problem with export function. Default setting - export function does not work. Any settings changes had no result. Application reinstall had no result, too. LMMS 1.1.0. It seems like a bug... Thanks for your job and help!
My system: win7 64 ultimate, creative fatality.
p.s. " I've found post on russian LMMS page on VKontakte with similar problem, without more discussion. Maybe it's only russian trouble? Ha-ha." - i am from russizn too.