I have a C program which calls various SP using isc_dsql_execute_immediate

for some reason, it sometimes gives

Database error code - 335544721
Unable to complete network request to host "localhost".
- Error reading data from the connection.

I cannot find any reason for this behaviour or any consistancy. Any
suggestions gratefully received while I still have some hair left.

Environment is fedora core 5, firebird 1.5.4