3:27a Pacific, I'm unable to even get your forums to load at this point... Is everything ok with your server?
Update: Evidently it took 4 minutes to load a 500 error.
Your main page loads, but takes quite a bit of time to load... Are you on a shared host by chance? It'd explain random load issues and your hosts ability to keep throwing memory at problems...
At some point, Shared Hosts (especially cheaper providers such as GoDaddy) will simply fail to allow your site to function optimally; generally overselling system resources and praying that things still function over time.