Rated 1 out of 5 stars

ThunderBrowse was an exceptionally useful add-on for Thunderbird, however neither this version nor v 3.7 that awaits review by Mozzila work with TB5.If ThunderBrowse is enabled no email message appears in the message pane. ThunderBrowse options can be selected but not actually implemented; only "Cancel" works on the Options window that opens.Please update this add-on to be fully compatible with TB5.Windows XP Pro SP3 • Firefox 5 • Thunderbird 5

This review is for a previous version of the add-on (3.3.5). 

Why don't you try 3.8? It should fix these problems.