ORA-03113 end-of-file on communication channel when running a query in the SQL Window (4327093)

Running a query in the SQL Window generates ORA-03113 end-of-file-on communication channel.
It does not seem to occur the first time running a query after opening TOAD, but if running the query again, the problem is reproduced.

If TOAD is shut down, returns thee the message, "Oracle has terminated the session or the connection is dropped!".
A core dump is produced on the UNIX server.
These core dumps will fill up the Oracle filesystem, causing Oracle to crash.
This problem occurs when connecting to multiple servers, all running Oracle 8.0.4.
It also occurs on multiple client workstations, some running Win2K and some running NT.

In the login menu, click on the "Show connection options".
Unchecking the "Force Sql Net" option and checks the followings:

Sql Net compatible Net 8
Build Oracle Alias list
Use Last Oracle Home

Warning: Checking the "Sql Net Compatible Net8" may affect the ability to view CLOB and other large objects.