The remote host is missing an update to squid announced via advisory DSA 077-1.
Vladimir Ivaschenko found a problem in squid (a popular proxy cache). He discovered that there was a flaw in the code to handle FTP PUT commands: when a mkdir-only request was done squid would detect an internal error and exit. Since squid is configured to restart itself on problems this is not a big problem. This has been fixed in version 2.2.5-3.2. This problem is logged as bug 233 in the squid bugtracker and will also be fixed in future squid releases.