Please note: Version 4.2.2 was never made generally available, so if you are upgrading from 4.2.1, see also 4.2.2 Changes. In particular, version 4.2.2 introduced support for 64-bit Windows.
Version 4.2.3 introduces support for Mac OS X 10.8 in addition to some new features and bug fixes. See 4.2.0 Changes for changes introduced in SICStus Prolog 4.2.