Success, I reckon
Well, I've spent the last couple of days doing computer maintenance. Deleted a lot of old files, defragged the C drive, etc. All of which gained me a lot of space to do things again. So now, I've finally installed Firefox as my browser, and voila!
I can post from my main computer without crashing LJ. Yay.
Although I really think it sucks that LJ couldn't/wouldn't/didn't find a way to make their latest update work with my ol' Mozilla browser. But, onward and upward. Maybe now I can do more with LJ again.