On my profile page, if I click on any of the last three tabs -- All actions, Responses, or Votes -- I get an error page. All the other tabs work fine. I think this is new within the last 12 hours or so.
I tested on several sites (Meta, Worldbuilding, Mi Yodeya, Community Building). At first I thought the problem was that "private" tabs were broken (you can't see other people's responses or votes), but actions are public so it's not that.
Odd exception: on English Language & Usage, All actions results in an error but Responses and Votes work for me. Other users (see comments) report different sites that do/don't work for them, so it's not a site-specific problem. I can't identify anything that's different for me among the sites I tried. (It's not moderator versus not; I'm not a moderator on Community Building or English.)