Tried safe mode -- same thing.
When I run with private browsing, it will work fine between 0 and 3 times. That is, sometimes it fails the first time, sometimes I can do it about 3 times and have it work each time.
But once it fails, it will no longer work (e.g. I can try 10 times and it fails each time).
I'll give it some time (maybe ISP will fix something), then try some more stuff. I use that button a lot.
With IE, I did it 10 times with no failures. My understanding is that IE handles file types differently -- this may or may not be relevant:
When you click on a link, your browser sends an http request. The system at the other end evaluates the request, then sends back an http response header attached to the return file. NOTE: this is in addition to any statements included in the <head> section of an actual html document.
Browsers handle the reception of the response header transparently so the general user is not aware of it.
One of the functions of the http response header is to define what type of file is attached, via a "content-type" (often referred to as MIME type) declaration - this tells the browser how to handle the file. It is this content-type in the response header (NOT the filename extension) that FFox uses to determine how to handle the file. It is the responsibility of the server housing the files to send an appropriate content-type in the http response header.
Sometimes the server housing the file in question may not be configured correctly and delivers an http response header with an incorrect content type. Files to be displayed as Html should have content type of "text/html"; plain text files should have content type of "text/plain"; executable files will have content type "application/octet-stream" or one more specific to the application.
If a file is served with a content type that isn't automatically displayed or handled by FFox, it will ask you what to do with the file. MSIE, on the other hand, ignores the http standards, ignores the http header content-type, and takes its own best guess on how to handle the file - consequently many server admins aren't even aware of the problem if they are serving the files with the wrong content type.
So if your file is being served with a content type other than "text/html" then TBird won't display it as a web page.
You can see what content type was received by FFox. Right-click on an empty part of the displayed page and choose "View Page Info" from the resulting menu. Under the General tab, look at the "type" line.
If you're not convinced (or don't trust what FFox tells you, or, as in your case, if the page isn't displayed by FFox at all so you can't view its page info), go to
www.web-sniffer.net and enter the URL of your page or link. Then scroll down to the reply header that is displayed and see what is listed as "content type".
If an inappropriate content type is being sent, contact the webmaster, as they need to fix this at the server.