Recently I faces a problem in admin module,  developed by some programmer that when I submit add entry button it adds two records but when I submit for Firefox, I was working  fine.
After 3 hour of mess I found error, In IE8 you have to return false, if you are submitting form through javascript. Here is example
<form name=”frm” onsubmit=”return chkForm();”>
function chkForm()
{
//Variuos checks
document.frm1.submit();
return false;
}