Admin cannot preview posts

Hi
I came up against a very strange issue. On my 3.2 Wordpress, only the SuperAdmin can preview a post. All other users below when clicking on Preview button receive the error: "You do not have permission to preview drafts.".

That is very strange! Any idea?

FYI
here are the WPMUDev plugins installed:
e-Newsletter
Create, manage and send beautiful HTML newsletters to users and subscribers from right inside your WordPress dashboard. Installation & Use Instructions »
Get Support » 1.0.2 1.0.2
Easy Google +1
Add the Google +1 button to your site and let your visitors tell the world how cool your site is! Installation & Use Instructions »
Get Support » 1.0.3 1.0.3
Membership
The most powerful, easy to use and flexible membership plugin for WordPress, Multisite and BuddyPress sites available. Offer downloads, posts, pages, forums and more to paid members. Installation & Use Instructions »
Get Support » 2.0.7 2.0.7
Pop Up!
Allows you to display a fancy popup (powered as a popover!) to visitors sitewide or per blog, a *very* effective way of advertising a mailing list, special offer or running a plan old ad. Installation & Use Instructions »
Get Support » 3.0 3
Ultimate Facebook
The only Facebook plugin you will ever need: Autopost to your wall or fan page, registration and login, Facebook comments, BuddyPress profiles support and more. Installation & Use Instructions »
Get Support » 1.0.9 1.0.9
Update Notifications
This required plugin lets you know when your WPMU DEV plugins and themes need to be updated, and even allows you to auto-update them... critical for security and functionality! Installation & Use Instructions »
Get Support » 2.1.3 2.1.3