Problem: XY events do not always appear as a selectable layer when connecting to an Access database using an OLE DB connection
When an XY event is created from a Microsoft Access database using an OLE DB connection in ArcCatalog, you may see inconsistency in your ability to set these themes as a selectable layer.
The tables stored in Access do not contain a field that ArcGIS can use as an internal ObjectID.
Solution or Workaround
Create a new field called AutoNumber in the table containing the XY event values, using Microsoft Access. This field will act as an ObjectID field for ArcGIS.