some kind of problem on my elgg site

i'm still having the same problem back when i was still with shared hosting, the problem is that at some point in the day, the site prevents users from logging in and registering. the only solution to fix this is to rename a plugin. i don't wanna have to keep on relying on this, because i won't be awake when people register or can't login when i'm away and what not. so can someone please tell me what's wrong with this? or is anyone having the same problem?