changing between 6.4.1 and 6.5

Hi List,

after an installation of PostgrSQL v6.5 on a new machine
i have problems with a view which is running without problems
under 6.4.x.
But the view isn't the problem. The same statement on the real table
realized the same error:
ERROR: illegal use of aggregate or non-group column in target list
(aggregates are not existing in my database)

Statement:  select x1, x2, x3, x4 on tablex order by x1, x2;

Know anybody somthing about that kind  of changing if it is a real one.

by Jens