This is coming from a few years ago when I had to work with SQL on $SOME_UNIX_VARIANT_NOT_HPUX. Anyway, [link|http://www.acronymfinder.com/af-query.asp?String=exact&Acronym=ISTR&Find=Find|ISTR] having to enter some SQL command like set escape [ so that whatever the default value is (quite possibly _) gets out of the way.
I'm not sure if it was truly "set escape" but it was something like that. Look into it, perhaps.
Also, if you don't have a login on [link|http://technet.oracle.com/|Oracle TechNet] I highly recommend it. Free as in beer.