Finally! Stupid power outage frying my stupid PSU. Well, that or it was already dying, and the power outage just made that evident. Oh, and then there’s the stick of RAM I discovered was bad. BUT, all is now well. Until the next thing breaks.
Turns out, after I upgraded to Apache2, I neglected to re-enable the suEXEC module, which meant that any attempt to save content to the wiki would have failed. My apologies to anyone who may have attempted to post a comment on any pages (for example, the savsender discussion page).