So i think he has 2.60b else server would say that you need another version of et..
but i think i had the same problem as you,
you probably have to re-install et new but just 2.55 for moment, and then fully update first to 2.60 and then to 2.60b you probably have some programs like et starter pro or smth
this wont help you.
So take here the patches and : 1. 2.60 2. 2.60b
Patches