Data provider internal error("-3000")

Sometime i get this error from OracleDataReader. I'm using asp.net and oracle DB 9.2 with Oracle Data Provider for .NET 9.2.0.2.102 I couldn't find any descriptive and logical cause for this error. Im using datareader to retrive a largea amount of records from the DB (sometime 400.000 records), but i can not see why this could be a problem, the whole operation takes 10-12h to finish, but sometimes it is succesfull. Memory consumption is low. I retrieve data and write them to a text file. Can anyone has some clue what coulb be the cause for this problem. Thanks in advance.