The HashCodeKeyGenerator class is producing inconsistent key values across VM restarts due to its use of:
(line 74) hashCodeCalculator.append(System.identityHashCode(method));

When running in Sun's Java 1.6.0_06 32-bit linux JVM, System.identityHashCode(method) is returning inconsistent values for the same method between two different runs of the JVM. The differing values means that none of the persisted (on disk) objects from the previous VM run are being matched up with their semantically identical objects in the next VM run.

Note: I am using Ehcache as the caching implementation.