Just a status report - for those Lindens and others reading these notes.
My system is an AMD Athlon XP 2800+ based m/c with Nvidia GeForce4 MX built in (motherboard) running Mandriva 2007.1 (Spring).
I couldn't get the above on-board graphics chip to work with Linux, possibly because it uses the 'legacy' drivers from Nvidia (1.0-9639). I got just a black window contents when I tried to start SL client. The chip seems to be identified as an nForce2 AGP by the system config utility. I did get that graphics chip to work with Windows XP (dual booted), but I never use that O/S normally.
The problem with that setup is probably NOT in the client, because when I tried to use Mandriva's 3d desktop features that also gave me a black screen when X started.
So I splashed out £20.00 and bought an Nvidia GeForce 6200 card (not exactly top of the range, but...) and installed the lastest drivers (100.14.11 ), along with Mesa and all the other dependencies and this works quite well enough for me. I can't use the 3D desktop - it seems to reduce the colour depth to 24 bits and SL tells me it needs 32 bits - but it does work OK when I adjust the settings. SL has given me no major trouble (apart from the stuff everyone else is suffering) in this configuration. I occasionally get scripting errors - but don't know yet what's causing them or whether it's the client or the server. They don't seem to stop me in my tracks, so I'm not too worried about them. Will try to investigate further.
Best Regards.