squid: timeout in SENT_PASV state

Hi all, please can somebody tell me what to do against this. Is this a ftp server that is not accepting pasv ftp? Or is it a misconfigured squid? Sep 29 21:23:54 gate squid[406]: ftpTimeout: timeout in SENT_PASV state Sep 29 21:24:18 gate squid[406]: ftpTimeout: timeout in SENT_PASV state Sep 29 21:24:41 gate squid[406]: ftpTimeout: timeout in SENT_PASV state Sep 29 21:29:03 gate squid[406]: ftpTimeout: timeout in SENT_PASV state Thank you all, Philipp