date fromat error in sql 2008

Question

my date selection format is  5/31/2012
  
inserting in  dd/MM/yyyy  format...

but if i select gridrow tat date is displayed in my textbox ... now if i select some other date t date format comes like 5/31/2012.


 so while updating that date value it shows error as

String was not recognized as a valid DateTime..

Any suggestion Please i m using sql2008 with Datatype Date