Maya booleans are terrible, they break 99% of the time. I would just merge them all into one object. Make sure said object is selected in object mode.
Then go to the top view turn on display>polygons>backface culling, go to faces mode, select everything using lasso, invert selection, now you should have the faces facing away selected, just hit delete and voila.
If there is too many faces selected and you are deleting faces you can still see you can shrink selection before deleting.
Last edited by Scruples; 03-15-2012 at 12:43 PM..