OCI Error in CDC Designer

Hello there,
i get this error while myservice tries to process data from an oracle database: "ORACDC508E:Oracle method OCIStmtFetch failed with error: OCI_NO_DATA".
The off thing is, after I started the service and loaded the initial data, the process runs for several hourse without problems. But after ca. 5 hours (or 20000 changes) it fails.

I hope you have an idea..

Regards