The error will appear in the data_engine log until you UN-check 'automatically reindex tables'. That should make it stop trying to index them.
Regardless, recommendation is to upgrade to NMS 6.2 to take advantage of the new database maintenance. It's likely that once you upgrade you can turn the data_engine reindexing back on.
'online' index rebuilds are not supported by SQL Server Standard.
online=on is only available in MS SQL Server Enterprise
Re Partitioning: Please upgrade to NMS 6.2 asap which contains a fix.
data_engine maintenance is completely re-done in NMS 6.2 especially regarding partitions and according to engineering is now "self-healing", so upgrading to NMS 6.2 is the preferred fix for partitioning issues.
The new maintenance routine will actually go through and find out if your partitioning schema is correct or not, and will fix it
If you are not not using SQL Enterprise you should NOT turn on auto-reindexing in the data_engine and you should instead have your DBA set up a nightly re-indexing job.
Please also find reindexing script attached that you can use for now prior to upgrading to NMS 6.2.
The query to run it in a job is:
exec [dbo].[DBA_RebuildIndexesBasedOnFragmentation] @maxfrag = 30.0, @databasename = 'NimsoftSLM', @rebuild = 1
(this will do table-locking rebuilds if the version is SQL Server Standard)
Note for the query to run successfully, change the database name if your database is not named 'NimsoftSLM.'