MIME issues with IE6

Question

I'm developing a web service that will allow my clients to download files of any type that are stored as binary data. Firefox 3.6.9 successfully prompts the user with the download dialog. However, my clients will be using IE6, which simply prints the binary data on the screen instead of prompting the user to download.

Is IE6 ignoring my MIME header? Is there some IE6 obscurity I'm not aware of?

Below is my MIME header. Files can be PDFs, text files, emails or any multitude of others. Any advice would be greatly appreciated!

<mimeHeaders>
     <content-disposition>attachment; filename=fname.ftype</content-disposition>
     <content-type>application/octet-stream</content-type>
     <content-transfer-encoding>base64</content-transfer-encoding>
     <content-id/>
</mimeHeaders>