It seems the non-linear sequence can be explained by the number of write operations performed on the CMP bean between inserts.
This behviour seems rather odd. Does anyone know the precise behaviour of "hsqldb-fetch-key"?
Appears to be a bug in the HSQL shipped with JBoss 3.2.4
The problem is resolved when I simply dropped in some new HSQL jar from JBoss 4.0.1