0 byte transfer and 550 error code

Ever since upgrading to this version of SmartFTP, I have been experiencing occasional 0 byte transfer problems which were actually fictitious. If I shut down SmartFTP and then restarted it, the uploaded file would appear on the server with the correct number of bytes and would render correctly on the web site

That is no longer the case.

0 byte transfers are now the rule and nothing I seem to do overcomes this. There is no upload occurring. I have contacted the host support people and they say that they have nothing at their end that is able to block a customer from uploading files. I have also tried this with the Firewall and Anti-virus software disabled with the same result.
Here is the log from the no Firewall+Anti-Virus attempt.

[10:53:34] SmartFTP v4.0.1142.0
[10:53:38] Resolving host name "home.comcast.net"
[10:53:38] Connecting to xxx.xx.xxxxx Port: 21
[10:53:38] Connected to home.comcast.net.
[10:53:38] 220 FTP server (Version 5.339PWS/AI) ready.
[10:53:38] USER Potomac_NMRA
[10:53:38] 331 Password required for Potomac_NMRA.
[10:53:38] PASS (hidden)
[10:53:38] 230 User Potomac_NMRA logged in.
[10:53:38] SYST
[10:53:39] 215 UNIX Type: L8
[10:53:39] Detected Server Type: UNIX
[10:53:39] RTT: 93.415 ms
[10:53:39] TYPE I
[10:53:39] 200 Type set to I.
[10:53:39] REST 0
[10:53:39] 350 Restarting at 0. Send STORE or RETRIEVE to initiate transfer.
[10:53:39] PWD
[10:53:39] 257 "/" is current directory.
[10:53:39] CWD /LayoutTours
[10:53:39] 250 CWD command successful.
[10:53:39] PWD
[10:53:39] 257 "/LayoutTours" is current directory.
[10:53:39] TYPE A
[10:53:39] 200 Type set to A.
[10:53:39] PASV
[10:53:39] 227 Entering Passive Mode (xxx,xx,xxx,x,xxx,xx)
[10:53:39] Opening data connection to xxx.xx.xxx.x Port: 55610
[10:53:39] LIST -aL
[10:53:40] 150 Opening ASCII mode data connection for /bin/ls.
[10:53:40] 226 Transfer complete.
[10:53:40] 15983 bytes transferred. (40.0 KB/s) (390 ms)
[10:53:56] TYPE I
[10:53:56] 200 Type set to I.
[10:53:56] SIZE Prior_Tours_02-04-11.html
[10:53:57] 550 Prior_Tours_02-04-11.html: not a plain file.
[10:53:57] File exist check failed. File not found or permission denied.
[10:53:57] MDTM Prior_Tours_02-04-11.html
[10:53:57] 550 Prior_Tours_02-04-11.html: No such file or directory.
[10:53:57] The operation has been added to the Transfer Queue. Check the Transfer Queue for

the status.
[10:54:10] SIZE Prior_Tours_02-04-11.html
[10:54:10] 550 Prior_Tours_02-04-11.html: not a plain file.
[10:54:10] File exist check failed. File not found or permission denied.
[10:54:10] MDTM Prior_Tours_02-04-11.html
[10:54:11] 550 Prior_Tours_02-04-11.html: No such file or directory.
[10:54:11] The operation has been added to the Transfer Queue. Check the Transfer Queue for

the status.
[10:54:19] SIZE Prior_Tours_02-04-11.html
[10:54:19] 550 Prior_Tours_02-04-11.html: not a plain file.
[10:54:19] File exist check failed. File not found or permission denied.
[10:54:19] MDTM Prior_Tours_02-04-11.html
[10:54:19] 550 Prior_Tours_02-04-11.html: No such file or directory.
[10:54:19] The operation has been added to the Transfer Queue. Check the Transfer Queue for

the status.
[10:54:28] SIZE Prior_Tours_02-04-11.html
[10:54:28] 550 Prior_Tours_02-04-11.html: not a plain file.
[10:54:28] File exist check failed. File not found or permission denied.
[10:54:28] MDTM Prior_Tours_02-04-11.html
[10:54:28] 550 Prior_Tours_02-04-11.html: No such file or directory.
[10:54:28] The operation has been added to the Transfer Queue. Check the Transfer Queue for

the status.

There are several back-to-back attempts because in the past, on occasion, instead of an immediate failed transfer, I would get a copy and replace prompt. Sometimes that worked, and sometimes it didn't. Now it never happens at all.

The last line of each failed attempt is incorrect to the extent that there is no visible evidence of the file information being placed in the transfer queue. The transfer queue appears empty.

Please post the log from the transfer: double click the file in the transfer queue. And please upgrade to the latest version of SmartFTP: https://www.smartftp.com/download/

Here is the log from the Transfer Queue

[12:21:04] Operation Begin
[12:21:04] Remote file exist check: "Prior_Tours_02-04-11.html".
[12:21:04] SIZE Prior_Tours_02-04-11.html
[12:21:04] 550 Prior_Tours_02-04-11.html: not a plain file.
[12:21:04] File exist check failed. File not found or permission denied.
[12:21:04] PASV
[12:21:04] 227 Entering Passive Mode (216,87,188,9,191,176)
[12:21:04] Opening data connection to 216.87.188.9 Port: 49072
[12:21:04] STOR Prior_Tours_02-04-11.html
[12:21:04] 150 Opening BINARY mode data connection for Prior_Tours_02-04-11.html.
[12:21:04] 35327 bytes transferred. (316 KB/s) (109 ms)
[12:21:06] 226 Transfer complete.
[12:21:06] SIZE Prior_Tours_02-04-11.html
[12:21:06] 213 35327
[12:21:06] Source File Size=35327, Destination File Size=35327
[12:21:06] Operation End

The entry in the Remote Browser pane is [Firefox Document Icon]Prior_Tours_02-04-11.html 0KB Firefox Document 2/5/2011 12:21 PM

When I tried to upgrade to the latest version of SmartFTP, I was advised that I needed to install SP3. I have SP2.
If I install SP3, it will cripple other software (which is no longer being supported) that I need. Can this be resolved without a SP2 to SP3 upgrade?

I dont see any errors in the transfer log. Try to manually refresh the directory after the transfer using F5 or the refresh button in the toolbar.

Refresh (F5) doesn't change anything. I think I may have a problem in my system somewhere. I've tried three other FTP packages with the same result.
Thanks

Try to temporary uninstall your software firewall and antivirus products if they are not from Microsoft.