Well, select the object you want to keep first then the object you want to make the intersection with. Then try the Booleans again.
One thing to note, is that the Maya Boolean feature can be very buggy, especialy in the earlier versions.
Also, instead of using intersection, you should use Difference.
Hope this helps.
www.stevenegan-cgi.com
"Your weapons are no match for ours! People of Mars, surrender!"
"Um, this isn't Mars. This is Earth."
"Earth? Earth-with-nuclear-weapons Earth?"
"Yes."
[long pause] "Friend!!"