this keeps happening :(
http://prntscr.com/6n2f5y
http://prntscr.com/6n2ffn
Please wait a bit at first launch. If you still have problem, uninstall completely (MLK Uninstall.app in your application folder, and delete personal preferences in "~/Library/Application Support/UltraStarDeluxe" (In finder, Go > Go to folder ... > paste this and press GO, delete everything you'll see in that folder)) and reinstall from MLK_SIM2.iso.
Also note that MyLittleKaraoke need at least the additional disc 1 and 2 installed to work on OSX since mavericks.