why does it do this?

Black lines appear and then eventuly the screen is completly covered so I have to re log in.
Why, what happens?

Sounds to me like a incompatablility issue with your graphics card. Has this happened every time that you have run SL or just isolated incidents.

That's what I was thinking also. Could you provide us with your computer's specs? Here is a link to the system requirement page.
http://secondlife.com/corporate/sysreqs.php
Hopefully your video card or monitor is not going out. Have you tried adjusting your computer's screen resolution?

I dont know about my specs, I could tell you them if you know how to find them on windows xp...

I will try different resolutions as well, because it happens on another online game I play.

You can go to the Start button, and right click on My Computer. When the menu pops up select properties. When another window pops up look under the General tab. Under this General tab will be some information about your computer such as your operating system, who the computer is registered to, the windows verification code (don't post that), your processor, and how much ram you have. What seems to be more important in your case is to find out what kind of graphics card you have and if you can change settings on it for better performance. It may not be compatible for 3D gaming.

Start button>Control Panel>Display>Settings tab

This should show you what kind of graphics card you have, color quality, and screen resolution. I think Second Life requires True color enabled or at least a 32 bit color quality setting. If you have a graphics card that is giving you problems with gaming, you may want to upgrade it will something better if you have a desktop or just buy another computer if possible. I think the most popular brand of video card I've seen other SL peeps using is Nvidia. You might want to check your manual, and read online what your machine is capable of upgrading to if the video card is going bad or inadequate.

P.S. You may just have to update your video card's driver in the device manager.

You can also get the most relevant PC specs to SL, from the Help menu on the client, under "About SL". I think that's the right place, it's definitely in the Help menu.

Gives details of processor, RAM and graphics card as I recall.

This sounds like it may be one of the common (yet often overlooked) flaws of the ATI 8000+ series. I'll await your reply with specs, and post accordingly.

Aha thank you Gaybot, well, I have a NVIDIA GeForce 6200 LE graphics card, and the colour quality was already at 32 bit.
I also have a Pentinum 4 CPU 3.06GHz,
3.06GHz, 1.00 GB of RAM
......if that helps in any way.

You seem to have good specs overall for your computer; but your video card, from what I've read, just meets the minimum requirements and is no longer mainstream. I think the latest Nvidia GeForce is model 8800. You could go to the Start button, right click My Computer, select Properties, and a window will appear. Click on the Hardware tab, and then click on Device Manager. You will see all of your hardware in this window such as your video card, power supply, disk drives, etc. Find your video card in the list; it will be named NVIDIA GeForce 6200 LE and may be under a section called Display Adapters. Once you find it, right click on it and select Update Driver. It will ask you if it is allowed to connect to Windows Update to find software; click Yes and Next. If it finds a better version of the driver for your video card, it will automatically download and install it. Then you will prob have to restart your machine. The Lindens say on the blog that updated drivers are important for your video card to function properly in Second Life.
Take a look at these links I found in these forums about your specific video card.
/111/8c/146377/1.html
/111/87/143341/1.html
/111/15/98348/1.html
/111/8e/90352/1.html
/111/ec/92520/1.html

It just searches my computer for a better upgrade ......and then doesnt find one. What the hell.

Im on the NVIDia site, will that help me?

Maybe your card is simply dieing ^__^

toasted graphic ram

Hmmm, I had trouble finding drivers for that specific model of graphics card. The closest thing I could find was this.
http://www.nzone.com/object/nzone_downloads_winxp_2k_32bit_91.31.html
I have made a post on your behalf in the technical forum. Here is a link to it.
/111/ce/169295/1.html#post1426066

i guesse my second question is, where do i install to? Because I tried this with a few others (not sure if this was one of them) and well, lets just say it didnt work and leave it at that.

I need to be told step by step.

Thank you so much Gaybot Foxley! Having followed your graphics driver update advice, I can finally see that Second Life is not composed almost entirely of grey rectangles!