Why can not &quot;open&quot; in IE?

Why can not "open" in IE?

guidance

It's very strange that the links, generated by my download code, can not be "open" in IE but OK for "save as"!
If I select "open", after clicked the link in IE, everything seems OK (filesize, progress bar etc.) but the file is always blank, no matter ZIP file or text file, only inline pictures are ok.

Please help!

My code:

ob_end_clean();
header("Last-Modified: " . gmdate("D, d M Y H:i:s",$openfilerecord['lastmodified']) . "GMT");
header("Content-type: $type");
header("Content-Disposition: " . ($inline?'inline;':'')
. "filename=\"$filename\"; size=$filelength");
header("Content-Length: " . $filelength );//attachment;inline;

readfile($fn);

Please kindly check my site to see the difference of "open" and "save as": http://citymap.dns2go.com/

guidance

If I put a direct link to my files within web document directory, it's OK, e.g. http://citymap.dns2go.com/download/partbeta191.zip
is OK for "open" in IE click, but if handled by my code in file.php, http://citymap.dns2go.com/_scripts/file.php?f=11 , the problem will appear!
That means my web server is no problem, but php is suspected.

guidance

Could anybody have a look at and give your ideas? Thanks!
http://citymap.dns2go.com/

guidance

Could you offer your download code for my try to find whether the problem is in the server config or my code?

Anon

its gota do with ur headers for the zip.. try pasting all of the stuff to deal with headers and output.

guidance

Below is all other statements in front of file.php by a 'require':

ob_start();
set_time_limit(300);
session_cache_limiter("private,max-age=1000");

session_start();

Then header and output from file.php:

readfile($fn);

guidance

I tried both apache2.0.36 and 1.3.24, same problem.
I checked both from my office and home, same problem.
Please help to check from your side: http://citymap.dns2go.com

guidance

Any problems in my code?