302 Found: "Document has moved" on redirects

I just reinstalled Zen Cart (1.3.9h) after transferring my domain name (cell-rehab.com) to iPage hosting. This is a fresh install (no addons, themes, or anything).

Whenever Zen Cart tries to redirect the page anywhere (in admin and in customer area), I get a 302 error.

Code:

0<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> <html><head> <title>302 Found</title> </head><body> <h1>Found</h1> <p>The document has moved <a href="http://cell-rehab.com/store/index.php?main_page=down_for_maintenance">here</a>.</p> </body></html>

(notice the "0" before "<!DOCTYPE...")

It's the same error as shown here http://www.zen-cart.com/forum/showthread.php?t=115359, except the solution in that thread does not apply to my situation.

To see this error, go to my storefront, http://cell-rehab.com/store (you will see the maintenance page), and click on any link that will redirect back to the maintenance page ("Continue" button for example).

Is this a problem I should take up with my hosting provider, or is it something I can fix? I've looked all over the internet and really couldn't find much on this issue. Thanks in advance