Read more at "Learn CSS Positioning in Ten Steps" tutorial
You need to be sure that you are forcing your launch to use a 32-bit VM. Apple ships most of their VMs with 32 and 64-bit binaries. To force the VM to run in 32-bit mode, use the -d32 option as VM argument in your launch configuration. Note that as of Snow Leopard (OS X v10.6) the default VM is 64-bit.