Bug 472703

Description of problem:
If you attempt to open the broken FTP
URL for the first time, firefox displays
the appropriate message box with an error.
This is fine. But try to open the same
URL the second time, and you see no error.
An empty FTP catalog is displayed instead.
The problem is that even if the link is
fixed on a server side (missing file added
on ftp), you cannot open it any more.
Firefox will still display an empty catalog.
To make the matters worse, it appends '/'
to the URL, even if it is a file link.
You delete it, but it keeps appending.

Version-Release number of selected component (if applicable):
firefox-3.0.4-1.fc9.x86_64
and some older ones too, since 3.0 I think.

How reproducible:
Always

Steps to Reproduce:
1. Try to open a non-existal file on some ftp
2. See the error message box, close it
3. Add the missing file on ftp
4. Try opening it again
  
Actual results:
You can't open the file any longer.
Firefox somehow remembers that it was missing.
You see an empty directory instead, but
the URL was the file link, not a directory.
Firefox keeps appending '/' to URL though.

Expected results:
Error messages, as long as the file is missing.
Opening the file, as soon as it was added.
NEVER mangling an URL by appending '/' to it.

Additional info:
This is really really very annoying bug to me. :(
I am increasing severity.
It is a problem also with the win32 builds of
firefox, btw.