Below are two screen images of the Forum Summary of the "Misc" Forum (text only view) within the "old skin" & the current skin taken at 18:19 (UK time) today,
You can see that there is "white" space around each of the thread titles as if the row height of the table rows are (now) too tall for the content, or the row spacing element has been changed.
The images are taken in Mozilla Firefox (for Windows) 13.0.1, but the same issue is present within Microsoft Windows Internet Explorer 9.0.8112.16421.
A "hard" refresh of each browser did not clear the problem.
NOTE: Just the [discussed] tab content is like this; the [new] (& [custom]) tab(s) are not affected.