I just went through a similar problem, but in my case the dreaded blank page did not show up for 2 weeks! And then, my solution was different. For whatever reason, my custom theme was causing the problem. (I tried the solution above but it did not help). I re-uploaded my theme from my private backup and the site showed up again.
Does anyone know what might cause this? Maybe a hack or a virus? I posted about it on my blog and it would be nice to be able to explain the problem.
