Excerpt from sf case: https://na1.salesforce.com/50030000000bw4l

We have a Big Application that are deployed as multiple WebApplications and they make crosscontext calls, When we enabled Clustering Seems like FirstCrossContext Failes on this Method.
JBOSSCacheManager.createEmptySession(). We would appreciate if you can help us resolve this issue.

Note: If i deploy this App on Default Server Configuration and it works fine

Basically, the problem is createEmptySession is treated as a un-implemented method since it is also called by passivation and activation. But we will simply return this method call now with a new ClusteredSession instance (depending on the granularity, of course).