ORA 24323 - Report Builder

Yesterday we encountered a weird issue with Report Builder. One of the developers, while working on a report, encountered the following error:

ORA-24323: value not allowed
==> select * from mytable

Report Builder: Release - Production on Thu Jun 12 10:10:05 2008

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Enter Username:
Program exited with status 1
Concurrent Manager encountered an error while running Oracle*Report for your concurrent request 4792266.

Review your concurrent request log and/or report output file for more detailed information.

The developer proceeded to make several changes but received the same error. Then they pulled up other reports and the error occured there as well. They contacted us thinking that there may be something wrong with the environment.

I have never used Report Builder but a quick search turned up 2 possible solutions:

1. A mandatory value received incorrect or null data.
2. Your not connected to the database in report builder.

I asked the developer to verify that the SQL they were working on was valid by pasting it into sqlplus and executing it and to verify that they are connected to the database.

A short while later they let me know that once you receive the error above, it seems Report Builder loses connection to the database. At that point they have to reconnect and if the query is fine they no longer receive the error.