b0d215b created the issue

Premise: MS Windows doesn't allow colons (:) in file names, but *nix does.

When I download a file from a Linux system that has a colon (:) in its filename to my Windows computer, I get an error message saying:

Cannot create file [filename]. Please contact your webhost for further Help.
(Or similar, my language is in German.)

The problem is that in this case the error lies not with the webhost, but with the local operating system. So I propose to check if it's a download or an upload and change the message accordingly. So for download it should rather be:

Cannot create file [filename]. Your operating system does not seem to support the filename.