I'm trying to use the TOracleEvent component to receive dbms_alert's, but it doesn't seem to work properly. Sometimes I miss alerts, and sometimes I get an ORA-03113 error. What's wrong?

Both Oracle8 8.0.4 and 8.0.5 have had problems with the dbms_alert package. There was a timing bug that could cause these kinds of problems. For 8.0.4 you need to upgrade to at least 8.0.4.3.2, and for 8.0.5 you need to upgrade to 8.0.5.1.1.