2 things to note:
I cannot purchase items from steam or itunes because they give me a "cannot find a secure connection" error.
At first glance, that to me indicates some sort of massive OS structure failure and / or massive viral / malware infection. however,
I recently reformatted and the problem still persists. Other PCs on my network do not have the same problem. I recently moved all of my components to a new chasis, and am wondering if the ethernet port or controller could have been damaged. If anybody could shed some light on this problem it would be greatly appreciated, as my PC has become almost unusable.
...indicates a troublesome driver
for your NIC and / or a major IRQ conflict on your system or
Get your HW checked (a *nix live CD / DVD is a good way to check it) - if all works well, then it is either your OS installation, or else something somewhere infecting you.
If you need to reinstall *again* make sure you use a completely different
to rule out (and help prevent future) infection.