Can't see any speedruns, just this error. Refreshing, deleting cookies, and logging out does nothing.

Notifications still work though.

Never heard of that one before, but I think I figured it out. How many games do you currently follow?

I checked the behavior of the front page - the page initially loads the header buttons and the news on the right side. Then there is a separate second call to the server (for the record: "ajax_latestleaderboard.php"), to get all the latest runs with regard to your settings: minimum and maximum followed games to display, as well as which games you follow. However, for some really weird reason all those settings are part of this call to the server; so the list of games you follow is part of the query parameters.

It looks like this: fg=19920,691,20710,21099,21459 (The numbers are the games' IDs)

To go back to my question: let's say you follow 1000 games, then all those games' numbers will be sent in the latest-leaderboard request, and the parameter will be at least ~3000 characters long. GET calls to the server are always limited by 2048 characters... and it appears you passed this limit.

If this is indeed the issue, then unfollow some of your games and see if that fixes it. You can also send a bug-report ticket in the support hub about this (feel free to refer to this thread for reference).