Fireball-192 jdbc4 driver error in Tomcat due to caches

Starting 27 Dec 2012 (GMT-8), many customers have received this stacktrace when trying to access admin functions or browse to GreenHopper:

java.lang.NoClassDefFoundError: org/postgresql/jdbc4/Jdbc4ParameterMetaData
    at org.postgresql.jdbc4.Jdbc4Statement.createParameterMetaData(Jdbc4Statement.java:46)
...

Also affects Confluence, creating a Comment will fail and pop up a red error box with a tracktrace with the same error.

Workaround: shut down the instance, wipe out the work and temp directories in the Tomcat directory (catalina-base) and start JIRA. Need to file HOPS ticket to request that this be done during upgrades anyway.