intermittent problem

I'm trying to correct a whole lot of files resident on-line.
Roughly every second time I open SmartFTP for this purpose, I'm unable to view, open or edit the files appearing in the left-hand folders: all that happens is an error message saying
What am I doing wrong, please ?
I apologise if I'm being idiotic; but I'm trying to get my late and beloved husband's site 100% correct, and not managing this very well.

I'm having the EXACT same problem.
I've added my log, just in case something obvious in there helps.

[09:11:00] SmartFTP v2.0.996.36
[09:11:00] Resolving host name "XX.XX.XX.XX"
[09:11:00] Connecting to XX.XX.XX.XX Port: 21
[09:11:00] Connected to XX.XX.XX.XX.
[09:11:01] 220 Serv-U FTP Server v6.2 for WinSock ready...
[09:11:01] USER XXXXX
[09:11:08] 331 User name okay, need password.
[09:11:08] PASS (hidden)
[09:11:08] 230 User logged in, proceed.
[09:11:08] SYST
[09:11:08] 215 UNIX Type: L8
[09:11:08] TYPE I
[09:11:08] 200 Type set to I.
[09:11:08] REST 0
[09:11:08] 350 Restarting at 0. Send STORE or RETRIEVE.
[09:11:08] PWD
[09:11:08] 257 "/n:/FTPRoot" is current directory.
[09:11:08] CWD /n:/FTPRoot/pub
[09:11:08] 250 Directory changed to /n:/FTPRoot/pub
[09:11:08] PWD
[09:11:08] 257 "/n:/FTPRoot/pub" is current directory.
[09:11:08] TYPE A
[09:11:08] 200 Type set to A.
[09:11:08] PORT 192,168,1,100,4,52
[09:11:08] 200 PORT Command successful.
[09:11:08] LIST -aL
[09:11:09] 150 Opening ASCII mode data connection for /bin/ls.
[09:11:09] 2462 bytes transferred. (160 KB/s) (15 ms)
[09:11:09] 226 Transfer complete.
[09:11:20] TYPE I
[09:11:20] 200 Type set to I.
[09:11:20] SIZE file.iso
[09:11:20] 213 361433088
[09:11:20] MDTM file.iso
[09:11:20] 213 20060711021639
[09:11:20] No rule matched. Default Action="Ask".
[09:11:22] PORT 192,168,1,100,4,55
[09:11:41] An established connection was aborted by the software in your host machine.
[09:11:41] Server closed connection
[09:11:41] Transfer failed.

The "No rule matched. Default Action=Ask" stuff is not error message, it's just an information.

@OldIron: In your case, the error is rather that "PORT 192,168,1,100,4,55" fails. Try connecting in pASV (passive) mode. Search the foum how to do that if you do not know.

@cmrstringer: To find out what's the real problem in your case, we need the log.