Forum OpenACS Q&A: Response to ORACLE occasional stream_write_lob error when downloading files

You problem may be solved by upgrading the Oracle DB to a 8.1.7 release (preferably Checking Metalink, I see that in they've fixed Bug 1418809, tersely described as:
OCI insert of a LOB can crash the client
Indeed, if I remember correctly, the AOLServer driver for Oracle is OCI-based. There's no guarantee that your problem will be fixed by upgrading Oracle alone, but I think it could be worthwhile.