Hello Claudio,
I had the same problem just yesterday:
https://openacs.org/bboard/q-and-a-fetch-msg.tcl?msg_id=0003Je&topic_id=11&topic=OpenACS
I want to run nsd8x instead of nsd76 and my site is using German characters.
To understand the full range of this problem, here a link from the aolserver mailing list:
http://www.mail-archive.com/aolserver%40listserv.aol.com/msg01669.html
Here some steps that I took. They might help you...
1.) Switched from AOLserver3.4 to AOLserver-3.3.1+ad13
http://www.arsdigita.com/acs-repository/older
2.) updated my aolserver nsd.tcl file like Harry Minski told to in:
https://openacs.org/bboard/q-and-a-fetch-msg.tcl?msg_id=0002YI&topic_id=11&topic=OpenACS
Read Jonathan Marsdens last response to the upper thread telling me about problems with ns_write and that those problems don't occur with ns_return....
So I tested ns_return and voila works, tested ns_write: Unluckily he's right... German characters are displayed correctly with ns_return, but not with ns_write... so I applied the patch #44 and got the same error that you got!!!
Finally I read through Tilmann Singer's post on the following thread:
https://openacs.org/bboard/q-and-a-fetch-msg.tcl?msg_id=0000oi&topic_id=11&topic=OpenACS
and know that he has everything up and running now, although he manually had to patch ad+12, which you don't have to do with ad+13 anymore!
I decided to put that effort on hold, because openacs 4.x will fully be .adp and not a problem concerning iso-8859-1 anymore (I hope)...
