OK. Completed the simple test which resulted in an error. The test was as follows:
a. Perform PST import in stages to populate different stores.
b. Took Zimbra down
c. Unmounted non-current store
d. Started Zimbra (no error reported on startup nothing untoward in zimbra.log)
e. logged into webmail account
f. searched for items prior to date (known to be held in non-current store)
Ah well.
