Finally got Second Life running.
Got fed up of getting "Window Creation Error" messages while running with Dapper 6.06. I upgraded to the Edgy 6.10 distro and SL ran straight away but with a rubbish framerate (jerky).
I upgraded the ATi drivers and now get excellent graphics and it runs extra smooth....
Ubuntu: Edgy Eft October 2006
Second Life: 1.13.2.12
CPU: Athlon 64 3200+ (754)
ram: 512 MB
Graphics: ATi Radeon 9600 pro 256mb
Driver:
OpenGL vendor string: ATI Technologies Inc.
OpenGL renderer string: RADEON 9600 Generic
OpenGL version string: 2.0.6286 (8.33.6)