Sorry, it took a while because microsoft insisted to install the famous IE bug fix
Anyway, I restarted, selected the earlier provided epub and just inserted (after a full stop) "<". From that moment on book edit (calibre-parallel) started eating memory, but not everything as the "memory error" happend after some time while there was still memory left (see picture).
I do not quite grasp what you mean with the ":" colon. My insert was somewhere in the text.