After upgrading from 7.1.8 to 8.3.42 I get the message
The FogBugz database is down or could not be found.
Error: -2146232009: ERROR [IM002] [Microsoft][ODBC Driver Manager] Data source name not found and no default driver specified
The sConnectionString value in the registry has the following value, for which the server and database are correct:
Server=S15360249\RS001;Initial Catalog=fogbugz;Integrated Security=SSPI;MultipleActiveResultSets=true;
I get the same error if I completely remove the sConnectionString entry.