Splitting > 1GB Files // Problem with FileStream class

Hi, in my Air (2 beta) app i'm splitting large files to upload them in  smaller chunks.

Everything works fine, until i choose files larger  than 1GB?

This might be the Problem:

var  newFile:File =  File.desktopDirectory.resolvePath(filename);                        
trace(newFile.size);

//  8632723886  (About 8GB correct file size)

BUT if i use the FileStream Class instead:

var stream:FileStream = new  FileStream();

stream.open(new File(filename), FileMode.READ);

trace(stream.bytesAvailable)

//  42789294 ("wrong" file size?)

If i run the same code with files smaller  than 1GB stream.bytesAvailable returns the same result as newFile.size.

Is there a  limitation in the FileStream class or is my code wrong?

Thanks!