Native Paul,
I have started a tutorial guide for the Gallery theme by Chris>
It still is a Work In Progress but covers certain aspects of installing and tweaking.
Currently it all from my experience of the theme, but slowly writing in some users tips too, which I would like to add you hack to.
Hopefully we can find a better solution for you.
I have the same issue, have deactivated all plugins and still not working, never even used Tweetable plugin though and still looking for a solution.
I forgot to mention, I have tested this in both Flock (default), Firfox and IE 7
OK, so i just renamed the related-posts.php to temp-related-posts.php, hit F5 and bam, Admin now loads with no apparent issues.
Additional tests to continue.
