JavaScript - Window.Open Will Not Work Twice

I have an aspx page with a button. When the user clicks that button, the following javascript opens a new browser window (in this case, 'Reasons.aspx'). Works great. Here's the function for that part:

function ShowPanel(url) {
var width = 750;
var height = 600;
var left = (screen.width - width) / 2;
var top = (screen.height - height) / 2;
[Code] .....

When this window pops up, there are some controls. One of which is a button, which triggers almost identical code to popup a third window (in this case, ReasonCodes.aspx). Only it won't work. Here's the code for that:
function fGetReasons(url) {
var width = 750;
var height = 600;
var left = (screen.width - width) / 2;
var top = (screen.height - height) / 2;
[Code] ....

I've set breakpoints on the javascript. It does execute. Here's what's weird -- The above javascript executes, only I don't get a new window with ReasonCodes.aspx. However, I set a breakpoint in the page_load of ReasonCodes.aspx and all of it executes. So the javascript executes, the code-behind page_load of the third page executes, but I don't get a third page. Instead, the second window (Reasons.aspx) refreshes. It's like my third window is somehow 'hidden'.