Weird problem with loading/rendering DOM

Weird problem with loading/rendering DOM

Hello,
i already spent more than 48 hours for this problem, and still no idea to solve it..

here's my scenario:
i have a function (i.e: getPreview() ) that load a preview of an image , the load are done with ajax. now getPreview() is triggered from a button (i.e: .renderbtn)

There's no problem with the above scenario, the problem arise when i want to build a button to show all preview.
Here's my function code:

function showall(){
                    $j.each($j('.renderbtn'), function(index) {
                        getPreview($j(this).attr('id'),'pin_tools','render');
                    });
                }

with the above, only the last item is rendered. BUT if i add alert():

function showall(){
                    $j.each($j('.renderbtn'), function(index) {
                        getPreview($j(this).attr('id'),'pin_tools','render');
                        alert('Display item :'+(index+1));
                    });
                }

eventthough there are alert, all display correctly...

Now, i'm thinking to pause the proses with this code:

function pausecomp(ms) {
            ms += new Date().getTime();
            while (new Date() < ms){}
        }

function showall(){
                    $j.each($j('.renderbtn'), function(index) {
                        getPreview($j(this).attr('id'),'pin_tools','render');
                        pausecomp(1500)l
                    });
                }


But the problem still arise, any idea what i should do ?

Thanks