Hi, just found this post having ecountered the same problem.
To me the bug seemed to be something with the footage and sequence settings.
It was a 4:3 project with a weirdo footage with something like 700×576, I was going to reframe it onto a 720 sequence.
After importing, as soon as I dragged the footage CS6 prompted me to choose between keeping the sequence setting or changing them in order to match the footage’ ones.
If I kept my sequence settings the rendering time became insanely long, almost crazy and definitely unworkable with.
If I changed the sequence settings to match the footage’s everything worked out smootly and without problems.
I know it seems crazy but that’s what worked for me, hope it helps.
P.S.I am working with an outdated win7 notebook with a core2duo 2,53 Ghz and 4GB ram and all the footage onto a lacie1Tb with esata..so problems with rendering were expected but this seemed to be the matter with my setup.