从sharepoint下载文件时出现随机错误

I am using Sharepoint 2007 to host Excel 2007 files generated by my App, so that internal clients can download them. However, I sometimes (and it seems random) the bigger files fail to download (Internet Explorer and Firefox claim the download was successful, but the size of the file is smaller than expected and it is not usable). The files in Sharepoint are fine, because sometimes they download ok (so after trying a few times I can successfully download any file).I am using Sharepoint 2007 to host Excel 2007 f