Hello Ola,
Thank you for your answer. Indeed the problem is related with the tcl version. With nsd76 there is no problem because the unicode internal representation for the tcl interpretter was introduced in 8.x. I just tested my configuration with nsd76 and it seems that everything is ok. BUT can somebody comment is there part of OpenACS which _needs_ some 8.x feature. If no using nsd76 can be acceptable temporary solution.
PS: I am interested in using OpenACS with Spanish.