Hi Sorry took so long to get back to you on this. Here is the additional information you wanted
What server type are you running your WordPress blog on?
Live Site Setup
Platform Type: Debian - Linux 32bit Apache 2
MySQL Version: 5.0.45
Perl Version: 5.8.8
PHP Version: 5.2.12
Server type: Ubuntu 8.10 running in VM VirtualBox
PHP Version: 5.2.6-2ubuntu4.6
Have you tried adding media in different browsers?
Just tested IE 8 and Chrome 8 still same issue blank popup window.
Do you have any other WordPress plugins installed?
Plugins Installed - live site and dev environment same
Akismet - Not Activated
All in one SEO Pack - Active
Google Analytics for WordPress - Active
Google XML Sitemaps - Active
JW Player Plugin for WordPress - Active
Lightbox 2 - Active
Limit Posts - Active
Member Access - Active
NextGEN Gallery - Active
Peter's Login Redirect - Active
Redirection - Active
TinyMCE Advanced - Active
Update Notifier - Active
User Role Editor - Active
WPListCal - Active
Can you think of any configuration differences between your development environment and the production environment?
If you asking for just WordPress there are the same. For Server one thing is PHP Memory Limit: Live 32M Dev 96M, also the server would be different just in general.
I hope this helps. Thank you for the quick response.