It looks like your reporting at least three different issues here, so it’s a bit confusing to try to understand the root of the problem, but I’ll see what I can do to help.
Regarding the system error of being unable to find the file. Are you using a removeable device or network attacked storage disc for your download location? If so, can you please try using a local disc and see if the problem is still present.
Also, understand that some file systems are limited in depth, so you may get such errors if the path is too deep. A simple solution is to use a folder on the root of the drive/device, such as c:\downloads, instead of something like c:\users\your name\my documents\my downloads\videos\tv shows (for example) This shouldn’t matter on a windows drive using NTFS, but with other file systems it can. Many external drives and NAS devices use other file systems, as well as older windows versions.
As for the Comet ID pane showing gargled text, this is usually an Internet Explorer setting at fault. BitComet uses IE to display some web content, and recent changes to IE have caused similar problems. There is an article on wiki.bitcomet.com dealing with this. Please review it and it will most likely help you resolve the problem.
As for your listening port problem, it sounds like you have it resolved, but please understand that this is a networking issue that it out of bitcomet’s control. By installing a router, you’ve created a LAN (local area network), and made yourself administrator of that network. Unfortunately that means it’s your responsibility to make sure that incoming p2p connections make it to the proper computer. If your router supports uPnP (universal plug and play), AND its both enabled and not blocked by any firewalls or security software, then bitcomet will attempt to use it to open your port for you, but in cases where this isn’t possible, or doesn’t work, the easiest way to resolve the problem is to setup portforwarding in your router.
Going back to the first problem. If it persists even using a local save location, then can you please post a screenshot of the error. We have guides for making and posting screenshots in our guides and tutorials section.
ps. I’ll also remind you that this isn’t your topic, but since it appears to be abandoned by it’s creator, I’ll allow you to seek support here, but next time please make your own topic.