It took some fiddling to get Second Life working with Ubuntu Feisty using the 1_17_2_0 version on an T60p machine. I had to upgrade the ati drivers to the most recent (8.35.5) I could find, and wierdly if I uncommented LL_GL_NOEXT which supposedly would make it more stable, then it froze X (just after the precaching finished) which required a reboot.
Today's update of 1_18_0_6 now crashes with the default settings. However, if I comment out LL_GL_BASICEXT which again would presumably make it less stable then it does work. Though I did find that I had to log in and out from a different computer first for my avatar first (but thats a longer story I suspect).
Has perhaps the the classification of which opengl functions are used based on those environment variables changes between 1_17_2_0 and 1_18_0_6? Is there any other info I can give which might developers track down exactly what is causing this? (Not that I'm complaining about how its working, just would be difficult for some people to get it running on t60p machines).