Dynamic Src Of IFRAME

I am ripping my hair out trying to set the src (location.href) of an
IFRAME that i show once a user clicks on a certain link:

function editTimeEntry(timeEntryID, dayID, e) {
var x = e.clientX;
var y = e.clientY;
ew = frames['editPop'];
eF = getObj('editPopID');
eF.style.left = x + 10;
eF.style.top = y + 10;
window.top.frames['editPopID'].location.href =
"controls/editPopup.aspx?id=" + timeEntryID + "&did=" + dayID;
ShowFrame();
}

function ShowFrame() {
if (eF.style.display=="none") {
eF.style.display="black"; // FF Drawing bug
}
eF.style.visibility="visible";
alert("Location:" + document.frames['editPop'].location.href);
}

When the IFRAME is displayed it just shows about:blank and not the
location.href I set for it. After the first time, i click on the same
link and it shows me the correct address in the alert box in
ShowFrame(), but the iframe remains blank.