Mac zip file download issue size greater than 2 gb with cURL

Question

I am creating an application with flex(sdk 3.5) for MAC which uses zinc-mdm,curl and flex 3.5 sdk. This application has a bookshelf(tilelist) displaying icons of the ebooks, which on clicking will first load the zip file from the remote location and then will display data.

On clicking the thumbnail the following cURL command is called by the flex application:

var commandString:String = "curl '"+_bFileURL+"' -o '"+_bTempFileName+"'";
mdm.MacShell.close();
mdm.MacShell.execAsync(commandString);
mdm.MacShell.onComplete = completeHandler;
mdm.MacShell.onError = errorHandler;

cURL downloads the zip file present inside the "_bFileURL" variable to a location "_bTempFileName" on MAC.

But when the zip file size is more than 1.5 or so, then the application gets blank completely whilst the downloading is going at the download location.

I am getting the current bytes saved on the disk by on a timer function:

var testTimerObj:Timer = new Timer(_timerInterval);
testTimerObj.addEventListener(TimerEvent.TIMER,downloadProgressHnadler,false,0,true);
testTimerObj.start();
_downloadTimer = testTimerObj;

private function downloadProgressHnadler(e:TimerEvent):void
{
    _downloadedBytes = mdm.FileSystem.getFileSize(_bTempFileName);
}

_timerInterval is 30 secs currently

If i try to log progress data inside the text file(log.txt) with cURL then also i do not get any error why the screen black out or some curl operation hanged off, as i do not get any error.

I have analyzed that the black out happens when the data saved on the disk just crosses 1GB limit.

Is this issue in any way related to curl or MDM download limit for MAC...??

I am using mac 10.8, flash builder(4), flex sdk 3.5.

Please help me out ...