in the onload event, you are using a column named Category:
onload="WA_setSelectionsInChildList(MM_findObj('Parent'),<?php echo $row_WADAnominations['Category']; ?>)"
using var_dump to write the contents of the WADAnominations recordset, i do not see a column being returned named Category. I see a column named CategoriesFullID, is that the one that should be used?
looks like it, if i change it to:
onload="WA_setSelectionsInChildList(MM_findObj('Parent'),<?php echo $row_WADAnominations['CategoriesFullID']; ?>)"
on load selects the Best Walking Safari form the category