I'm using VS.NET 2003, SQL Server 2000.

In my case, the error "internal connection fatal error" was being generated when using a DataReader to read the field values of a record. As I stepped through the code in the debugger I was also getting an "arithmetic overflow" error when calling GetDouble on a field. As I looked further it turns out this field in the database table for the given record had the value "-1.#IND". I'm not sure how that value got there but once I delete the record the error went away. So essentially the "internal connection fatal errror" exception was masking the root cause.