in the ASP.NET AJAX Extensions 1.0 (RTW) the JSON format have changed for serialization of date datatype.
\/Date(123)\/
prior it was
@1211212@
Both uses a count starting from Jan 1st 1970
If you have build your own method based on jscript eval your application will fail. The recommended way is to use Sys.Serialization.JavaScriptSerializer.deserialize
which encapsulate a regex replacement.