In case anyone else has this problem... two bugs have been filed with SUN
Bug ID: 6747176 Make HTTP session versioning thread-safe
Bug ID: 6747179 cached session incorrectly removed in edge case
The bugs were not available on SunSolve at the time of this posting.
[Message sent by forum member 'jfaldmo' (jfaldmo)]
http://forums.java.net/jive/thread.jspa?messageID=299149