Why is it that when i click on a gui element it sends a mousedown and mouseup to the LAST gameobject that i clicked?

if i click a gameobject then proceed to click on a gui element it will send a mousedown and mouseup to the last gameobject clicked.

this does not happen in windows but does in android..... i,m stuck and cannot release my app uggggh.

using unity version 4.5.2f1

i have reproduced this with a single gui button element and an object with mousedown /mouseup script on it.... click the object (have it hilite itself) then click on gui button and see prior object recireve mouse events AGAIN!!!! uggg

please help, Cheers Bruce