What happens if you change:
<input type="hidden" name="AvatarFileName" id="AvatarFileName" value="<?php echo $row_WADAmember['AvatarFileName']; ?>" size="32" />
to:
<input type="text" name="AvatarFileName" id="AvatarFileName" value="<?php echo $row_WADAmember['AvatarFileName']; ?>" size="32" />
does the AvatarFileName text box have a value?