var objImgAvatar = $("#imgReceiverAvatar");

if(receiverOnlineUid == 0)

{

objImgAvatar.attr("src", "images/anybody_avatar.gif");

}

else

{

// this line will be crashed

objImgAvatar.attr("src", "usr/get_avatar.php?online_uid=" + receiverOnlineUid);

// this line work fine

$("#imgReceiverAvatar").attr("src", "usr/get_avatar.php?online_uid=" + receiverOnlineUid);

}