Only got it to work once...

AMD Duron 1.10 GHz
768 RAM
WinXP Pro SP1
NVIDIA GeForce3 Ti 200

Alright. I know my system specs aren't great, but anyway.
I only got SL to work once. Here's the average history of what's happened so far:
I originally logged into SL, and could hardly see anything in the training island. In fact, all I could see was the sky, water, and land (or what seemed to be the land anyway, although, when I got it to work, I saw that it wasn't at all the same thing).
Now, SL had mentioned on boot-up that my SiS AGP driver was outdated (I figured I'd try first, since updating drivers on this computer hasn't always been such a smooth process.), so I updated that, and SL was working perfectly.
At some point, though, I decided to quit for some reason. When I came back in, SL was back to the same behaviour as it was before. A friend who was trying to help me out suggested I also update my graphics card driver to a newer one as well (which I did -- from 53.03 to 56.72, their suggestion). This doesn't seem to have helped any.

Of note:
- SecondLife.log is FLOODED with the following message (Note: There are other warnings too):
WARNING Setting subimage on image without GL texture
- Mouselook instantly kills SL.
- Teleporting also kills SL (although that was working at the same time the display was)
- All chatting functions are working
- I've tried: reinstalling SL, deleting the cache

Any ideas?

Apparently that warning I quoted above appears when I've got SL minimized. I guessit's irrelevant, then.

I'd like to know what these are about, though:
INFO Key up event missed, resetting

I've managed to make SL work a second time, but I'm not sure how I did it.

It seems I had to get the server's attention somehow, as though it didn't know I was there.

What kind of network connection do you have? Is there a wireless network involved?
Do you experience "static" on the screen before SL crashes? Does it lock up your computer?

Internet -> Router -> Router -> PC
I've also tried running SL on my laptop, with much better results (Internet -> Router ))) Laptop).
My PC uses only wired, but my laptop was working fine with wireless.

There is no static (as far as I recall or have witnessed so far, anyway), and it doesn't lock up my computer.
From what I can tell, on my PC, I am not receiving data back from the server (I initially thought nothing happened when I tried to move, but friends have told me that I DO move, despite SL saying I haven't). My local firewall grants all in/outbound access to SL, and my routers have been configured to port forward anything back to the PC (despite the laptop not having needed this second treatment).

I've tried connecting my PC, via wireless, to the first router, and now it works.
I guess the second router isn't liking SL for some reason, or something like that...
Anyway... I guess that works as a temporary solution.

What brand and model of router is it? Is it possible you have the ports blocked?

"Internal" (inner network): Linksys BEFSR41
"External" (outer network): Linksys as well, but I don't remember the model number offhand.

I strongly doubt the ports are blocked. As I said, I had port forwarding on for the ports specified in the faq, and this still didn't solve the issue, YET when I connected through the external router instead, it worked.
This is strange, because I've never had this problem before. It may be related to UDP, though, and completely logical (I haven't really done extensive tests - most games I play use or support TCP, so I may have been unwittingly (or have been forced into) selecting TCP every time).

Wait, so you have TWO routers in series? That could certainly explain the problem you're seeing. Why do you have it set up that way, anyway?

Yes, two routers in a series. It does NOT explain the problem, actually, seeing as I've not had this program with any other game or program. (Port forwarding worked, at the very least.) Heck, I can get file transfers to work in MSN Messenger, of all things! (It's easy to set up ICQ, but MSNM?)

I have that set-up due to the way the two networks are placed and organised in my house. Unless I buy a whole lot of Cat5 and pass it through the cold air return (a real pain in the ass just to get ONE cable across), it's going to stay that way, too.