whats the correct way to modify jasperreports server date format

hi all

I had problems with a report i was testing which selects data based on from to dates entered by user... the query expects the database data in a format dd/mm/yy

the report built in studio works fine, but when published to server produces nothing

the one thing i noticed is that the dates entered on the server are displated as yyyy-mm-dd

so i changed the properties.config file to dd/mm/yy and now the report wont run it gives the following

i get access denied .... then dialog message 

The system was unable to complete you request. Your conversation may have ended, expired, or been invalidated

so changing the four date field seems to have screwed up the server

any help would be gratefully received

many thanks

george