So while doing research on what processor and memory I might be able to shoehorn into my darling little computer, I discovered new drivers for my network card.
These drivers promised increased speeds, reduced latency, and better diagnostics of network behavior.
They lied like rugs.
Since installing the drivers at 8:00 last night I have had no connectivity on my main machine, and I have spent majority of the last 24 hours doing nothing but trying to fix it.
I even went so far as to drive out and buy a new network card, only to discover my model is not the common SN25P but instead the very rare and poorly documented SN25Pa which has an AMR slot where all the documentation say there should be a PCI slot.
I have one last thing to try, and then it looks like I may have to do a full wipe and reinstall, which makes me very very unhappy.