The last Windows Update was on April 27th which is 2 days after this problem started (at least for me). Before that, it's April 12th, and I'm sure things were fine after this date. I tried rolling back the April 27th update anyways (even though it's applied on both the working and non-working computers) - the problem still exists.
I have the same problem (no post, no FTP upload, no MySQL updates) on my wife's desktop computer. So the only working computer I have is my laptop. I'm afraid to break it, but I might have to in order to find the culprit.
I can FTP & SCP fine to other servers (on the non-working computer); it's just coppermine-gallery.net where I have the problem.
I figured out a work-around for the FTP upload problem (on the non-working computer). Using SmartFTP 2.0.996, I can upload large files using Active Mode (PORT). When I initiate an upload, it seems to stall for about 10 seconds, then it transfers the file fine. Using SmartFTP 1.0, I cannot connect using Active Mode, and for most FTP sites, I cannot use Active Mode either. Passive mode (PASV) is usually what I use to connect and this works fine on the working computer. I have a router for my home-LAN, so using Passive mode makes sense, as far as I understand how Passive mode works. Maybe SmartFTP has some sort of mumbo-jumbo it uses to get Active mode working in version 2. In version 1, it tries to use an "ip-repeater" through SmartFTP's server when using Active mode (it fails though). In version 2, I don't see this "ip-repeater", but the pause of 10 seconds makes me think something is going on behind the scenes.