It’s fairly clear that something happened to begin blocking traffic.
The first suspicion that pops into mind is a software firewall. They can have exactly this effect, because they monitor outgoing traffic as well as incoming.
That is a supposed good, because it lets you block the bad stuff like adware “phoning home”. But this assumes you can tell the good stuff from the bad stuff – and most people can’t. So in order to be “safe”, software firewalls will pretty much block anything they aren’t explicitly told to allow through.
“But you told your firewall to allow BitComet”? Well, um, no, you just think you did. You once told it to allow a certain executable file, of a certain size, with a certain hash, through. This particular executable has a different hash, a different size, so it isn’t allowed through. Filename? Oh, no, don’t pay any attention to filenames, those can be faked, y’know.
It’s an update. You know it’s an update. I know it’s an update. Your firewall, though, doesn’t know from updates. It’s a different size, a different hash, it’s not allowed through.
The firewall in your router doesn’t try to control outgoing traffic. It diligently monitors incoming traffic, and because it’s external it can’t be compromised or subverted by any software you run on your computer. But it doesn’t try to stop outgoing communication, that’s not its job. It relies on you to keep your system clean, to make sure you don’t have nasties phoning home. As you certainly should.
If you are benefiting from a software firewall – if you actually read and understand those warning messages, and know what you are allowing, and haven’t long since gotten in the habit of saying “Allow” to its incomprehensible nags, then having it may be a good thing. Otherwise, you’re better off with the firewall in your router. (No router? Then this discussion doesn’t apply to you. Go away and forget you read this.)
Your firmware firewall won’t notice or care about future upgrades, and you won’t have to re-solve this issue every time one of your clients is updated, or your firewall is updated, or one of those sneaky Windows updates comes along and changes your settings to What It Knows Is Best For You.
So delete and remake all of your firewall rules. Check and recheck that you haven’t installed a new firewall you aren’t aware of, or that one you turned off hasn’t been reactivated. (Both of those happen a lot.) Consider ditching software firewalls altogether, and go with the firmware firewall in your router. It will protect you without sabotaging you.
