The crashes we're experiencing intermittently appear to be due to memory errors. Too much stuff getting loaded up all at once, I suspect. I confess I wonder if our policy of keeping every old post is going to screw us in the long term.
Almost certainly will.
You might need to think about having an offloaded 'old posts' different forum.
Iago, are you hosting? or colocating? or something. IE: is the box yours? and do you have access to another one. Or is this a hosting service and they gave you an account.
If it's the former, you might want to think about moving the database that the forum runs on to a different server. Therefore splitting the "application" load from the "Database" load. Although, I've never gotten a SQL querry error so it sounds like you're not using a BB that uses a database backend.
That's another possibility. Consider switching to a more robust BB server.
I've built web server farms before. If you could use some help figuring something out, send me a PM
I assume though, you know lots of geeks who also have done stuff like that, so.. I won't get offended if you don't.