might give you a hard time. In fact, it looks as if many problems of this type have been reported to the provider of the digital library software the vLib portal is based on.
Internet Explorer 7.0, by default, does not automatically prompt users for download of file resources without their consent.
Unfortunately, vLib tends to send the download request "en passant", and is unable to repeat it (or present a page that contains a link to the file resource) after users have confirmed the download.
A massive but efficient response is turning on automatic download prompt – see http://vlib.mpg.de/vlib-browser-notes.html
Still, some versions of IE 7.0 may claim to be unable to find a file resource on the server – which is not true, as apache logfiles clearly indicate that the resource has been delivered. However, IE 7.0 is likely to be unable to cache it properly, and hence does not "find" it.
No apache settings that influence caching were apt to solve the problem. An update of IE 7.0 is probably a good idea in this case. Comments welcome.
A fix has been announced for the next minor release of the MetaLib software, so that file resources may be downloaded, even though a download has been tackled by IE 7.0’s security mechanisms.