Hi Henrik,

2014ko urriak 8an, Henrik Singmann-ek idatzi zuen:
> 
> I unfortunately can confirm that org-babel-R-initiate-session contains
> the lines you mentioned at exactly 15 lines down. Deleting ob-R.elc
> (which was of the same date as ob-R.el) didn't affect anything as did
> reloading org uncompiled (C-u C-c C-x !).

I could reproduce this, also with recent git org and ESS.  It looks like
ESS is doing more complicated things, necessitating a more thorough
check that the session is in fact ready.

Can you test the attached patch?  It fixed the problem for me.