Greetings . . . I am kicking the tires on a freshly upgraded system (7.5.8 to 7.7.5).
One of the first things I wanted to check out was image handling. When I visit the Attachment Manager (from a Gallery Forum or a Discussion Forum) the pop dimensions are unusable.
It works just fine here - a second screen shot attached to the original post. Behaves the same with Chrome and Mozilla on Inliners test system - leading me to believe it is server side.
Using the old style the Forum renders the way it always did - but interferes with the Attachment Manager popup.
When using same code fitted to a 7.7.5 template - it just creates a gap at the top of the page - with all the of image overlayed entirely further down the page. And sure enough steps on Attachment Manager pop up.
Thanks for the hint! You're dealing with a noob here. Would have never have thought to go out to PHP and fit it there. But it was kinda nice to sit in the Style editor tweaking the margins and check results with the Preview button :-)
Therein lies the problem, we use lightbox to display several pages as "popups" within the software; if you take a gander at /templates/default/filemanager.tpl you'll see that we pull a full set of html headers for the filemanager popup, so making adjustments to the body class is going to reflect every embedded page.