On 14 oct. 2012, at 15:52, Wolfgang Schuster <wolfgang.schuster@gmail.com> wrote:
[…]
I don’t know if the bug was also in the stable but it’s in the beta version I use. You can use the following example to check for the bug:

\starttext
\placeontopofeachother{A}{B}
\stoptext


Hi I can confirm that the bug is present in recent betas, that is 
\placeontopofeachother
is broken, but Context version 2011.11.29 works fine with your example.

Best regards: OK