I came across a problem when using FlashDevelop where I couldn't see the trace statements being traced out. I had the latest Flash Debugger player installed so this wasn't the problem. I also had the Flash log viewer open (View > Flash Log Viewer). I found out that you have to click the little ‘Start tracking’ button on the Flash log viewr for the trace statement to be shown.
However, upon reading the FlashDevelop documentation I discovered the Flash tracer is disabled by default. Another way to get the trace statement to show is to go to Tool > Program Setting. Then click on the FlashLogViewer from the plugins sections. Under the ‘Misc’ option there is a setting called ‘Start Tracking’, click on the drop down menu and select ‘onBuildComplete’. Your trace statements will now appear in your Flash log viewer.