I think the compatibility thing is a red herring--the STOPLIST keyword wasn't introduced until SQL 2008, so presumably one of the things that a database in compatibility mode 90 has to do is ignore the fact it's a keyword so it doesn't break old code.

Out of interest, why are you only using either STOPLIST or the fully-qualified name with square brackets? Have you just tried enclosing STOPLIST in square brackets and not bothering with the whole database.table.schema stuff?