I am pretty sure that this is not related to XenForo as I am facing a similar problem with WordPress on the server I have. Importing process sends me to a 404 page after just a couple of seconds of running. Importing users form my old database too 1.5 hours and probably 100 attempts. WordPress does the same thing randomly during the post publishing process. I understand that if MySQL was at fault, the error would be visible on the screen and I would not really get a 404. But in my case, I am sent to the 404 page of the forum/blog. My server guy could not find any problem with mysql operations on the server. I am pretty confused and frustrated. Anyone here could guess what could be wrong? I have APC Cache enabled but I assume that it is supposed to do good things to your server and not bad!