I have a periodic problem accessing the forum from the links on the main page (the 5 most recent replies), in multiple browsers.
However, if I go to the dropdown menu at the top and access the forum that way, everything seems to work. It fixes itself throughout the day, but wondering what is happening?
It's the 404 page that you are getting, which is strange. I checked the script for the latest posts links, and it seems to be fine, even though I may try to change the default links to https. Since I am not able to recreate the error you're getting, please let me know if you keep having this issue!
If/when you do get the 404 screen, could you copy the URL address in your browser at that time and post it here?