@Asombroso That just means the site is very busy and burdened with heavy traffic. It happens periodically and shows up more often when large events are going on. Your best bet is just just refresh and the site will start to load again as it frees up resources.
Hmm.. at random times throughout the day I get "the site is under pressure" page to. Usually a quick refresh fixes this, never got the 405 error so I have no clue. I noticed the one time I was making a post and i got the site under pressure message but my post still went through, my guess is that it doesn't effect posts? I think the OP meant he already had cookies enabled and site just kept logging him out. Frustrating, I know. :(
The 405 is basically the same warning it just happens when you’re sending something to the server (like creating a forum post) rather than retrieving data for it. It looks like the site only did a custom error page on the retrieval of data, not sending it.
The same thing applies, just refresh (and agree to send your form content again) and it will eventually go through.
Also yes, these workarounds suck, but staff is aware that they have load issues, so I can only assume it’s on their roadmap to address in the future.