Well, just in case anyone cares: I just spent about half an hour hunting down a bug which first seemed to prevent me from correctly uploading a file to an FTP server. As it turns out, the upload was fine, the download with ReceiveHTTPFile() was the problem - whenever there was a space character in the filename.
Probably rather obvious, but with the forest and the trees... You know ^^ Simply replacing the space character with %20 will fix the issue - like this:
ReceiveHTTPFile(ReplaceString(url$, " ", "%20"), destination$)
Maybe this will save someone some searching. Maybe it's even worth a small note in the PB help file.