Fair point there - I was actually beginning to think the same - that it is a plugin interfering.
To answer your question: no, I don't use the same plugins on the test site as I do on allaboutarsenal - I don't use any on the test site, but dozens on allaboutarsenal.
I can't really think of which one could be having problems though...
Here is a list of all the (active) plugins on the website:
AddThis for WordPress
AddThis Smart Layers
Akismet
All In One WP Security
AutoChimp
bbPress
bbpress Simple Advert Units
BruteProtect
BuddyPress
Contact Form 7
Edit Author Slug
Embedly
Feedweb
FeedWordPress
Google AdSense
Google Analytics
Hyper Cache
ImageInject
Jetpack by WordPress.com
Leadin
Light - Responsive LightBox
Login With Ajax
MailPoet Newsletters
P3 (Plugin Performance Profiler)
Polldaddy Polls & Ratings
PopupAlly
Really Simple CAPTCHA
Regenerate Thumbnails
Revisionary
Simple Page Ordering
Speed Booster Pack
Statpress Visitors
Stop Spammer Registrations Plugin
Super Socializer
Use Google Libraries
WordPress SEO
Wp-Insert
WP-Mail-SMTP
WP-PageNavi
WP101 Video Tutorials
WPFront User Role Editor
WP Sitemap Page
WP Smush.it
WP Widget Cache