After a crash or power loss, Moneyworks will normally recover unsaved changes from the session file the next time a document is opened. There is a confirmation UI if you open the file directly. If the file is opened in Datacentre, then this happens silently.
It is not always the case, but the session file format can sometimes change between versions (6.1.1-6.1.2 was one such occasion). In such a circumstance, the session file produced by the older version of the software cannot be used by the updated version.
Therefore, as a general rule, if you get a crash that is going to require session file recovery, do the recovery before updating the software to a newer version.