Thread:Project:Current issues/Source parser extension tag seems to be broken

The rendering of text marked up with the parser extension tag seems to be broken on this wiki. See, for example, Manual:Tag extensions. The dashed-line border is being displayed (on FF3.6.3 for Windows XP, anyway) as an empty box above, instead of a border surrounding, each code snippet. This doesn't seem to be true on, say, the English Wikipedia; see, for example, Java (programming language). Anyone know what's causing the problem on this wiki?