[JamesAB]

Thanks for the info TheLastSuperman.

However, in this case it is a software issue not a server issue. I'm aware of the compatibility mode work around, but that isn't a very elegant solution. I don't like idea of telling thousands of members to change their browser settings because we can't get our code working right. I want to fix things properly on our end and that means dealing with all the quirks in different browsers.

I don't have a fix for Firefox 39 yet, but this simple change seems to make the file names appear correctly in Internet Explorer without having to enable compatibility mode.

Look for this in attachment.php:

// Opera and IE have not a clue about this, mozilla puts on incorrect extensions.
if (is_browser('mozilla'))
{
	$filename = "filename*=" . $filename_charset . "''" . rawurlencode($filename);
	//$filename = "filename==?$stylevar[charset]?B?" . base64_encode($filename) . "?=";
}

And change it to this:

// Opera and IE have not a clue about this, mozilla puts on incorrect extensions.
if (is_browser('mozilla'))
{
	//$filename = "filename*=" . $filename_charset . "''" . rawurlencode($filename);
	//$filename = "filename==?$stylevar[charset]?B?" . base64_encode($filename) . "?=";
	$filename = 'filename="' . str_replace('"', '', $filename) . '"';    //This works in IE
}

I'm only running this on my test server so far and I'm not calling this a permanent solution until I find out (and fix) why Firefox stopped handling file names as expected.

Thanks,
James