Compatibility Update for Serialization
Last week we released a fix for serializing data between .Net 4 and previous versions of the framework. Cross-version serialization allows you to write binary data with one version of the framework and read it with another, even if the reader is the older version. Although we can obviously try to work around as many issues as possible when releasing a new version, it's much harder to make changes that require updating one of the old versions.
This fix addresses some known incompatibilities with serializing binary data using .Net 4 and deserializing it using .Net 2 or .Net 3 on Windows XP and Windows Server 2003. On Windows Vista and Windows Server 2008 you just need to have the SP2 update for those systems.
The downloads for the fix are going out through Windows Update but you can also get them here.