1script - 5:25 pm on Aug 4, 2012 (gmt 0)

@backdraft7 : I'm seeing exact same pattern here, it's uncanny. Great conversion rates all through end of July and Aug 1st, then zombies appeared en-masse on Thursday (Aug 2nd) and haven't go home yet.

Do you have any data on where your non-converting visitors are from? I'm still trying to wrap my head around this phenomenon but it looks like they are probably from a wrong geographic region, although I'm not sure if it's as simple as that.