File complete, but Transfer Fails?

When downloading a large file, I consistantly get a ' Transfer Failed' message although the file appears to have downloaded ok. This seems to be more of an issue on the server side - not sending what I believe should be a 200 status after the file downloads (ftp log below). I have access to the ftp server (MS) and the router (Cisco 2611).

Any suggestions on what could be cauasing the 'Transfer failed' message even though the file has downloaded? I appreciate any help - seeing the failed message is not going to work for my client.

[16:13:01] PORT 192,168,1,5,5,145
[16:13:01] 200 PORT command successful.
[16:13:01] LIST -aL
[16:13:01] 150 Opening ASCII mode data connection for /bin/ls.
[16:13:01] 114 bytes transferred. (N/A/s) (0 ms)
[16:13:01] 226 Transfer complete.
[16:13:17] TYPE I
[16:13:17] 200 Type set to I.
[16:13:17] SIZE
[16:13:17] 213 508185054
[16:13:17] MDTM
[16:13:17] 213 20060506192548
[16:13:17] PORT 192,168,1,5,5,147
[16:13:17] 200 PORT command successful.
[16:13:17] RETR
[16:13:17] 150 Opening BINARY mode data connection for bytes).
[16:28:41] 508185054 bytes transferred. (537 KB/s) (00:15:23)
[16:29:41] Timeout (60s).

[16:29:41] Active Help:
[16:29:41] Client closed the connection.
[16:29:41] Transfer failed.

Use the Transfer Queue for all your transfers.

The control connection has been closed by your router - during the data transfer. Therefore no RETR reply will reach the client after the transfer is finished. The problem has been discussed several times.

Solution: Use the Transfer Queue

A lot of routers we have tested have these problems. They cannot assign the control connection to a running transfer (data connection). And as a result they close the control connection after a certain time (timeout).