Memory problem - how can i clean it ?

hello,

i have a problem ... i have writen a piece of code do make me an "animated" banner (hiding and showing layers..because every image as a diferente link)... with javascript ...

it works fine... but it has a problem... in about 10 to 15 min time the memory that the PDF uses can go up to 450 megs... an more before it crashes...

the problem is with the function that i use (see code in the end of the message) ...if i turn it of the PDF only uses about 30 megs (and it doesent go up) and stays stable.

can anyone help me with this?
Thanx

///////////////////////////////////////// javascript code

if(theClockTimer)
app.clearInterval(theClockTimer)
var theClockTimer = null;

var zzz = 28;

function roda()
{
var ocgs = this.getOCGs();
for (var i=28; i<31; i++)
ocgs[i].state = false;
ocgs[zzz].state = true;

if (++zzz == 31)
{
zzz = 28;
}
}
app.setInterval("roda();",1000);
roda();
theClockTimer = app.setInterval("roda();",1000);