FTP Connection issues

I am a first time poster and am not well versed in FTP problems. I set up a small website with 8 network cameras (on different networks). Each camera FTPs images to my Yahoo Small Business server. They have been working fine for years and I have not changed any hardware. 2 of the cameras recently stopped working. They have been tested and appear to working properly with the correct FTP settings. They work fine if plugged into another network. I then tried to access my server using FileZilla from the inoperative locations. That also failed. The internet is working fine at those locations. When I go to another location, FileZilla works fine with the same settings. When I attempt to connect at the inopperative locations, I get an error that says something like Ecconreset, failed to list directory.
Both of the inoperative locations are using DSL connections in fairly remote areas, but I have others on DSL connections. Not sure if that matters. Any help or suggestions would be appreciated, thanks.

I would reboot the dsl modem and any other equipment that the camera is attached to.

If the same credentials work when connected to another internet connection you know that there is something preventing FTP on that connection.

Filezilla says that there is a piece of hardware misconfigured see this really unhelpful bug note http://trac.filezilla-project.org/ticket/5661

What hardware do you have behind the camera? It may have died on you, or the DSL provider has made some changes that prevent you from FTP'ing on that connection all together. Once you can plug in your laptop to that connection and get filezilla to connect your camera will work. I suggest troubleshooting with your laptop connected because you have more options to investigate what the issue is.