CaloTriggerTowerService used to read LArTTCellMap via a conditions callback. This is not thread-friendly, so it was changed; it is now retrieved from the detector store during event processing. However, this can lead to the I/O system triggering the creation of TClass instances for the LArTTCellMap persistent classes, and TClass has been observed to sometimes malfunction when created in a MT context (at least as of root 6.22.00). The resulting dictionary failures were causing jobs to occasionally crash with bad_alloc exceptions. Try to fix by forcing the needed TClass instances to be created during initialize.