Same thing here.
Wordpress: 3.5
Wordpress SEO: 1.3.4.4
And my sitemap (http://www.motorsportmusings.co.uk/post-sitemap.xml) is completely blank.
I've deactivated all my plugins and reverted back to the Twenty Twelve theme and it has made no difference.
I have even contacted my webhosts to see if they could increase my memory allocation, but according to them I'm on a shared package so it wouldn't be the case.
Have to say that trawling through similar threads online and not seeing a solution is very disappointing - not to mention a waste of time - so I, and countless others, would appreciate it if a solution could be forthcoming sooner rather than later...