Normally I use Firefox 3 (on Windows) and until now never really noticed this, but there's a "dead spot" on the main article links above the category link. For example, the link "AMD Phenom II X4 955 Black Edition for AM3" has a dead spot in "tion for AM3" that goes about halfway up the text. I poked it with the Web Developer plugin (highlighting the current element), and it looks like it's the .taxonomy span taking up that room. Looking at the CSS for it, it's got a 1.5em padding around the whole thing, and the top padding is what's causing the dead space. At least in the Edit CSS functionality (which occasionally differs from changes to the "real" CSS), changing the padding definition from "1.5em" to "0 1.5em" (only have left and right padding) fixed the behavior.
Even odder, when I looking at IE7 to see what its behavior was, if I move the cursor over any of that text, the linking behavior goes away. Strangely enough, I can click the link when the cursor first enters the anchor's space, but if I move even a pixel beyond that, I can't click it anymore. Weirdest thing I've ever seen, and I can't even begin to come up with an explanation (other than the standby "IE sucks", which while true doesn't really advance a solution).
Safari 3 (Windows) and Chrome exhibit the same behavior for me as Firefox 3.