ERROR: ExecEvalAggref: no aggregates in this expression context

Hello,

Can someone tell me what this error message means:
==========
ERROR: ExecEvalAggref: no aggregates in this expression context
==========

Does it mean that there aren't any aggregate in the expression
context when there should be. Does it mean there are and there
shouldn't be?

For that matter, what are aggregates and in what expression
context should they be or not be in?

Could it be because I am trying to group around something like
entry_view.minprice,
entry_view.maxprice
where minprice and maxprice are defined in as
min (item.item_price) as minprice,
max (item.item_price) as maxprice
when the entry_view view is defined?

Thanks

--
Paul McGarry mailto:paulm(at)opentec(dot)com(dot)au
Systems Integrator http://www.opentec.com.au
Opentec Pty Ltd http://www.iebusiness.com.au
6 Lyon Park Road Phone: (02) 9878 1744
North Ryde NSW 2113 Fax: (02) 9878 1755