I experienced the same problem.
If installing on Windows with the following versions, the problem is caused by Zen cart checking for new versions.
Server OS: Windows NT EMG-ADELMO 5.2 build 3790 Database: MySQL 4.1.18-nt
PHP Version: 4.4.2 (Zend: 1.3.0)
PHP Safe Mode: On
Zencart: 1.3.9d
In your shop/admin/includes/header.php file, remove or comment out from line 141
// ignore version check if not enabled or if not on main page or sysinfo page
if ((SHOW_VERSION_UPDATE_IN_HEADER == 'true' && $version_from_ini !='off' && ($version_check_sysinfo==true || $version_check_index==true) && $zv_db_patch_ok == true) || $version_check_requested==true ) {
to around line 174
$url=(isset($_SERVER['REQUEST_URI'])) ? $_SERVER['REQUEST_URI'] : zen_href_link(FILENAME_DEFAULT);
$url .= (strpos($url,'?')>5) ? '&vcheck=yes' : '?vcheck=yes'; if ($zv_db_patch_ok == true || $version_check_sysinfo==true ) $new_version = '<a href="' . $url . '">' . zen_image_button('button_check_new_version.gif',IMAGE_CHECK_VERSION) . '</a>' }
As always, remember to make a copy of your original file before making any changes.