I had a quick look in the oracle docs, and that error isn't explained any further than the message you're already getting. I had a quick look on Google and Google groups. There is some info about it but it all appears to be dependant on what you're accessing Oracle with (Perl, VB etc).
Maybe there will be something there that can help more?
I am using netscape 4.06, 4.73 & 4.76 to access data using OAS and PL/SQL through a webpage and all is returned fine. When using browser version netscape 4.79, sometimes queries are fine, but on other terminals queries return the following error:
ORA-02005 "implicit (-1) length not valid for this bind or define datatype"