Problem Viewing Directory Listing

[nanis]

I've had a look through the FAQ and forums, but couldn't spot an answer to my problem. I was using Filezilla without any hassle, had it open and was working on my site. I tabbed to a different window and back again and found Filezilla had frozen. I closed and re-opened it and when I re-connected this is what I got.

Status: Connecting to ftp.*****.com ...
Status: Connected with ftp.*****.com. Waiting for welcome message...
Response: 220---------- Welcome to Pure-FTPd [TLS] ----------
Response: 220-You are user number 6 of 50 allowed.
Response: 220-Local time is now 06:29. Server port: 21.
Response: 220 You will be disconnected after 15 minutes of inactivity.
Command: USER *****
Response: 331 User ***** OK. Password required
Command: PASS *******
Response: 230-User ***** has group access to: *****
Response: 230 OK. Current restricted directory is /
Command: FEAT
Response: 211-Extensions supported:
Response: EPRT
Response: IDLE
Response: MDTM
Response: SIZE
Response: REST STREAM
Response: MLST type*;size*;sizd*;modify*;UNIX.mode*;UNIX.uid*;UNIX.gid*;unique*;
Response: MLSD
Response: ESTP
Response: PASV
Response: EPSV
Response: SPSV
Response: ESTA
Response: AUTH TLS
Response: PBSZ
Response: PROT
Response: 211 End.
Command: SYST
Response: 215 UNIX Type: L8
Status: Connected
Status: Retrieving directory listing...
Command: PWD
Response: 257 "/" is your current location
Command: PORT 192,168,1,5,6,99
Response: 200 PORT command successful
Command: TYPE A
Response: 200 TYPE is now ASCII
Command: LIST -a
Response: 425 Could not open data connection to port 40631: Connection timed out
Error: Could not retrieve directory listing

I don't think it is a problem with my firewall or router, as none of the settings were changed between the time Firezilla was working and when it wasn't (five minutes at most). The -a after LIST looks different, but I don't know what it is or how to get rid of it if it is the problem. It also says I am user 6 of 50 allowed, but I'm the only one accessing it.

Does anyone know what might have caused the problem and why it was working fine one minute and not the next?

Thanks in advance.

[botg]

It is a problem with your firewall/router. Please try to toggle passive mode in the settings dialog.

[nanis]

Ok, first things first, I got it working again, thank you. But it wasn't as straightforward as switching to passive mode (or at least not as I read the FAQ).

When I first switched to passive and set the port range, after making sure they were open on the firewall and router, it caused another error.

Transfer channel can't be opened. Reason: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.

Error: Could not retrieve directory listing

I remembered the description of the program picking a port above and below, so I tried switching the connection port from 21 to one within the range I specified earlier. This resulted in unable to connect errors, but when I switched the connection port back to 21, everything was fine again.

Any clues as to why that was what it took to make it work? I'm honestly curious, because I'm still baffled as to how it stopped working when none of the settings had changed.