Long story short, I got a new (semi-nice) computer, decided to get back into Blockland, now I'm having some issues.
Starting a game and playing, everything is fine. However, as soon as I place or load any bricks, I get the infamous polygon stretching glitch...
You know, the one that looks like this.

I updated my drivers. I re-installed. I don't have any add-ons to remove other than RTB, but I experienced this problem before installing it.
And I know about the "flushtexturecache();" command. It worked for me on past machines, but now it does nothing; the above screenshot is after I performed that "trick" twice, and it didn't change anything.
--System specs--
Model: Dell Optiplex GX620 (office model inherited from a friend; changing graphics card is not possible)
Operating System: Windows XP SP3?
Processor: Intel Pentium 4CPU 2.8GHz (2 CPUs)
Memory: 2GB/2046MB RAM
Graphics: 128MB ATI RADEON X600 SE
I've also attached my console.log; you'll notice that I did indeed try "flushing the texture cache" at least twice. It had no effect.
I'm usually pretty good with issues like this, but I'm stumped. Any help is greatly appreciated.