As of JBoss AS 5.0.0 Beta3, the annotations package for such commonly used annotations as @Service and @Management have moved from the org.jboss.annotation.ejb package to the org.jboss.ejb3.annotation package. Additionally, the annotations have moved from jboss-annotations-ejb3.jar to jboss-ejb3-ext-api.jar which can be found in the client subdirectory.
You will need to change your code's import statements as well as recompile your @Service beans with the new JAR to have them deploy as they did in AS 4.2.x.
Attached, you'll find an example @Service bean project that demonstrates use of the new package. It was built with Java 6 against Java 6-compiled libs.