TraceOutputFileEnabledto 1 instead of 0. Then restart your browser and execute your flex program again.
# Beginning with the Flash Player 9 Update, Flash Player ignores the TraceOutputFileName property.
# On Macintosh OS X, you should use colons to separate directories in the TraceOutputFileName path rather than slashes.
TraceOutputFileName=C:\Documents and Settings\<username>\Application Data\Macromedia\Flash Player\Logs\flashlog.txt # Set TraceOutputFileName to override the default name and location of the log file
ErrorReportingEnable=1 # Enables the logging of error messages. 0/1
TraceOutputFileEnable=1 # Enables trace logging. 0/1
MaxWarnings=100 # Sets the number of warnings to log before stopping.
PolicyFileLog=1 # Enables policy file logging
PolicyFileLogAppend=1 # Optional; do not clear log at startup
Now open the C:\Documents and Settings\<username>\Application Data\Macromedia\Flash Player\Logs\flashlog.txt file in text editor and you should see the trace generated by your flex program. Other option is to use FlashBug which is a plugin in firebug