"Lunatic at Large" follows a group of strangers, one of whom has escaped from a nearby mental hospital
The interest and B.O. are there, but space is still too limited.
"Half-Blood Prince" drops 64% but remains box office champ.
Guinea pigs take in $32.2m to land top spot; 'Harry' pockets another $30m.
Sony's Katherine Heigl-Gerard Butler romcom staves off lukewarm reviews to open strong.
