Trace() won't work

Trace() works in 2.0 files, but not in 3.0 files. Why?

EDIT: actually I just realized that I added a “C:\Documents and Settings\Account1\Desktop\” classpath to Edit>Preferences>Actionscript>Actionscript 3.0 Settings> and that’s why I am apparently not able to use trace() any more. I took the classpath out, but now I can’t use the package and classes in my file because it doesn’t know where it’s at. How am I supposed to tell it where my AS file is yet still use trace()?