Force Download with multithreading downloader?

[eluser]Unknown[/eluser]
The force_download helper seems not work fine with multithreading downloader, such as flashget. Only using borwser internal downloader in single thread is fine. But with multithreading downloader, the final file that downloaded will be damaged and the data is wrong. Fore more, the download page will be excute for many times also. Any ideas about this problem?

[eluser]Unknown[/eluser]
I found why, because there was an error or notice or warn output so the download file was wrong. SOLVED!