This error is displayed when you have reached the max table size for the 'events table', this table logs all Yellowfin events (e.g. login, startup etc...). The table size limitation is only present in the evaluation/demo version.
The only resolution is to re-install Yellowfin using a full-release.
If you are after a full version, please contact firstname.lastname@example.org and include your company information so you can be contacted, and a full version can be organized.