At least on some machines I use (various versions of M$ IE on at least three different PCs), the "Forum Description" is in a smaller font, and therefore doesn't affect line height -- it's narrow enough always to be a single (not very high) line. What *does* sometimes vary (on my laptop, I think, since that's the smallest of the screens I use [I usually maximize the window]) is the "Last Post" column's date-and-time display: when the first coumn goes wider to accommodate an LRPD, it pushes the intervening columns right so the last column gets narrowed enough to split the date and time onto separate lines. This being two lines of a "standard-size" font, it's higher than the height of (Forum title) + (Forum description) over on the left, and therefore increases the table's vertical spacing.

One "solution" would be to futz with your zIWT preferences (what stylesheet to use, if any, etc) and your browser preferences (allow stylesheets, allow page-specified font sizes, etc) so the Forum description is always in the same font size as Forum title (and date and everything else); that way, it won't matter for the total height of each (logical) Forum row whether the date-and-time is displayed on one (physical) line or two. Another would be to go back to an older browser (or set your new one to work) like Netscape 3 or something, where tables are rendered only after all their content has been downloaded.