There are several ways to fix overlapping images when using isotope. The problem comes when the isotope event triggers before the images sizes, font sizes and other divs are not yet known. Isotope’s own faq’s tells you how to fix this with their layout method. But it also depends on how you’re calling your jQuery, and your functions. Working with WordPress, I usually put all my custom jQuery functions in a file and load them with

$(document).ready(function () {
   // everything here
});

But if you’re using isotope layout method, the only thing I’ve found to work is:

$(window).load(function () {
   // everything here
});