ArcMap Crashes with ArcGIS has encountered serious error when Accessing Classified Symbology

Why does my Arc GIS keep crashing?

The most likely cause is the current default printer. ArcMap checks the margin, page size, and resolution of the default printer when starting up. If the driver or printer returns bad information, this can cause ArcMap to crash.
 

How do I stop ArcGIS from crashing?

To prevent crashes, ensure that you have installed the latest ArcGIS service packs and patches and that any add-ons or extensions are compatible. In addition, when editing, you may want to run the Check Geometry and Repair Geometry tools to find and fix any data problems that could cause software issues.

How do I fix errors in ArcGIS?

Errors can be corrected by making edits to the feature geometry, attribute values, network rules, or subnetwork definition. The next time the network topology is enabled or validated, the features with errors are evaluated. Dirty areas that have associated errors will remain until the error situation is corrected.