How the installer works is it downloads a list of checksums and checks if files on your computer match that checksum. If not, it tries to download the new file and then makes sure the new file matches.
My first judgement would be that there is an update coming to cRPG and they are in the middle of uploading files with a slow connection to the mirror without taking it down first from the public for some reason and thus the new mirrors.txt does not match.
That said the issue could probably also arise from the installer being unable to overwrite the old file due to the user being dumb and not running it as an adminstrator or something and having Warband installed in some protected folder (like Program Files). Though if it has worked before this is a bit queer.
I ran a test fresh install of cRPG to test though and it finished without a hitch so yeah, just remove your cRPG and reinstall I guess. EDIT: Or the problem has been fixed by the patch or whatnot finishing uploading obviously.
