If you are working with RockWorks16, Level 5, and a SQL Server database, you may see this error if you are using one of the Borehole Manager query tools (View | Filter Boreholes or View | Select Boreholes), applying a Polygon Region query, AND your borehole names contain a "#" character (such as DH #1).
The next public upload of the program will contain a fix for this. It has to do with the different characters that Access and SQL use to mark date fields, and we were filtering out the "#" characters which in turn mucks up the borehole names.
In the meantime you'll need to perform the query with a rectilinear or circular region (which function differently), or remove the "#" characters from your borehole names.
Molly Mayfield
RockWare Inc.