HTTP headers, IE and downloading

I'm writing a script to view/download an email-attachment. If the file happens to be an MS Word document and the browser IE (only tried with 6.0), then the download fails. If I choose to download (Content-Disposition: attachment; filename="whatever.doc") then only a part of the file (2/3) is saved to disk. Of course viewing the file doesn't work either. It doesn't seem to matter what I set the Content-Type to since IE seems to ignore that anyway, however I've tried application/msword, application/octet-stream and some others. I've tried all the things said in the comments to the header-function in the online-docs at php.net. I know my Content-Length header is correct and the whole procedure works great with Netscape 7.0 and if the attachment is a zip-file or a jpeg-image it also works in both IE and Netscape. Let's just say I'm stumped and I have googled for a solution for a long time and would be very happy if someone had one... Thanks in advance /Andreas