Trace Files are fullfilling filesystem

After updating my database from 10.2.0.3 to 10.2.0.5 one database server creates sql_trace files for every session, which connects locally via embedded SQL, although the system parameter sql_trace is set to false just as the session_parameter. Other servers which work whith the same ORACLE_HOME are working properly. I tried to switch tracing off with setting the event 10046. Also I tried the dbms_monitor package and the dbms_system package too, but tracing is continued. CAn anybody tell me, if there is a flag to be set or unset or if I can do anything else?  The performance is issued by disk