Massive lag spikes since d/ling 1.7.2

Minecraft worked fine before the latest update patch. I could run without any issue with default resource, or one of several resource packs (Fairelight 128 was my favorite). I ran it after running McPatcher 4.2.2. Never an issue, could run totally maxed out with graphics at around 200 fps.

I've upgraded to 1.7.2; big issues. Let's start with that I've run with what I had. After about a minute of playing, my game would suddenly massively lag out. I've heard the term "slideshow". I noticed my frame rate would hover between 1 and 4 or 5 FPS. I tried minimizing all settings. I tried just looking down at the ground. I've tried running patched for an HD pack (Fairelight), and then tried unpatching...and running the default Minecraft. All to no avail. I can load minecraft, it will play fine for a minute or two, then massively spike with lags, and frame rate reaches 0-5.

I've ensured I've upgraded my video card to the latest driver. That has had no effect. All my other games (Skyrim at max settings) work fine.