Forum OpenACS Q&A: Re: Selecting an empty (null) oracle-clob crashes AOLserver on Linux
Also, I don't whether or not there are any potential incompatability issues between 8.1.6 and 8.1.7 versions of the client vs. server libraries, like you're using. If you haven't already you should probably look into that. But without knowing more, I'd assume that just upgrading everything to 18.104.22.168 would be a good idea.
(Then finally upgrade to 9.x along with the rest of us sometime later, of course...)