Which model Mac do you have? That's the most important issue. Go to your Java preferences ->
Setting up Java for Leopard (see 2nd image) and see if you have Java 1.6 (also called
Java SE 6) listed. If Java SE 6 is not listed, then you cannot use LW 5 & would be restricted to LW 4 pro.
If yours shows the 32-bit Java SE 6, then move that up the list to the top of preferences to use, depending on which Mac you are using. If using an intel computer only a couple years old then use the 64-bit java instead. MacBooks made longer than a year ago would only be able to use 32 bit java.
OSX 10.5 Leopard only has 64-bit Java SE 6 so only the 64-bit intel computers made in past few years would be able to have Java 6. All other previous macs are 32-bit architecture.
OSX 10.6 Snow Leopard has both 32-bit
and 64-bit Java SE 6.