PDF generated on the fly and Safari on Yosemite

[jbv at souslelogo.com]

Hello list,
I have several lc scripts on a server that generate pdf files "on the fly"
when triggered from a html page on a client PC or Mac.
Everything has been working fine for years (meaning the pdf were
displayed or downloaded, depending on the OS or the browser).
But suddenly, on Mac OSX 10.10.3 Yosemite, with Safari 8.0.6
 (10600.6.3), the downloading stops working and Safari displays an
error message, something like "Safari cannot open the file xxx.pdf
because it's still downloading"...
Everything still works fine with Chrome and Firefox on Mac, and with
any browser on Windows.
Here are the few lines of code that set the content of the header of
the pdf :
put header "Content-Type: application/pdf"
put header "Content-Length : " & number of chars of myPDF
put header "Content-Disposition: attachment; filename=" &quote&
maRequeteName &quote

Any idea about the origin of the problem ?
Thanks in advance
jbv