Freeze/crash problem with nv4_disp endless loop error

I hope somebody else has had this problem, because I've just started getting it, and it's making SL unplayable for me at the moment.

I have Windows XP, my graphics card is Nvidia GeForce FX5200, the drivers are version 8.4.2.1, dated 3/9/06, downloaded from the Nvidia site. I had to install these new drivers after the 1.10 update, because my previous ones wouldn't allow me to see both the new lighting and ripple water. I got the usual 'not Windows logo verified' (or whatever it says) message when installing the drivers, but some searching on the Nvidia page assured me that it was OK to install them.

I haven't had any trouble before today; a little more lag, but otherwise everything was fine, the new drivers were working great. So, this morning I went online and almost right away started having problems: I kept freezing up, even when there were only three or four people in the sim, in *any* sim.

Every time this happened, I would totally freeze, I wasn't able to move at all; it was like a crash, only the screen stayed stuck on one view and the game didn't quit. This happened three or four times; a couple of times I finally had to turn off my power strip in order to restart my computer, because nothing else worked.

A couple of other times, I got a blue screen with an error message about the nv4_disp file, saying there'd been an error and Windows was shutting down to prevent damage; it said something about the file being in an endless loop. (I Googled this file name, and apparently a lot of other people have had the 'endless loop' problem.)

I have no idea what to do here. The drivers I'm using are the latest ones, I've tried reinstalling them but it doesn't seem to help. I've run Windows Update also, with no improvement. I'm really mystified; I had no problem at all before today, it just started doing this out of nowhere.

Does anybody have any advice about how to prevent this problem? Do I have to go back to the older drivers and give up ripple water? I hope the solution isn't to buy a better graphics card, because it'll be a while before I can afford that.

I'd appreciate any help anybody can give me; I'm reluctant to go back into SL until I can get this sorted out and be sure it won't happen again. Thanks a bunch in advance!