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 likeentry_view.minprice,entry_view.maxprice
where minprice and maxprice are defined in asmin (item.item_price) as minprice,max (item.item_price) as maxprice
when the entry_view view is defined?
Thanks

-- 
Paul McGarry            mailto:paulm@opentec.com.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