Symptoms
An error "canceling statement due to statement timeout" occurred. Initial investigation (kb #11174) showed that the reason is two blocking transactions.
Resolution
Find the blocking transaction
In order to find the blocking transaction, you need to find the blocking statement. This will be a similar SELECT ... FOR UPDATE statement that was executed earlier than the one that was canceled due to timeout.
If postgresql logging is enabled according to kb #121028, then search for the blocking transaction in postgresql logs (/var/lib/pgsql/data/pg_log/). If not, it is required to search the blocking transaction in PBA logs. If you find two blocking statements, check under which methods they were executed, search Parallels knowledge base for existing issues with these methods. If nothing found or you did not manage to find out the conflicting methods - feel free to report an issue to Parallels Support for more detailed checks.