problem of import wmv etc.

[HBB Alfred]

hello
i have one wmv.
i tried to import them by importFile,but nothing happend
var result = fl.getDocumentDOM().importFile("xxx.wmv");
fl.trace(result);

then i set the second parameter "importToLibrary" true, it's ok the video file can be imported.
fl.getDocumentDOM().importFile("xxx.wmv", true);

i found that encountered not only with the wmv file, other of wmv or avi files has yet

i don't know is there a bug?