Там на чистом английском языке в багах альфы написано, что с родным драйвером нвидиа x сервер валится, потрудитесь уж или прочитать то что там написано перед скачиванием (да хотя бы через гуглепереводчик) и перед обновлением также уж желательно на соответствующую страничку заходить.
http://www.ubuntu.com/testing/lucid/alpha1#
The nv driver used by default for nvidia video chipsets on the LiveCD is reported to lead to X server crashes. Investigation of this issue is ongoing and should be resolved for Lucid Alpha 2. As a workaround, users can boot with safe graphics mode" to use the vesa driver. (494627)
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The firmware for the bnx2 driver is not available on the alternate and server installer images at install time. This bug will be resolved immediately after alpha 1. As a workaround, users can install using the desktop images; or install using the alternate or server CD and enable the network after installation. (494052)
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Manual partitioning in the graphical installer is reported to cause the installer to crash. Investigation of this issue is ongoing. (494608)
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Clicking on the installer icon on the Kubuntu desktop CD fails to launch ubiquity. As a workaround, the installer can be launched from the commandline by running kdesudo ubiquity. (494997)
# The Kubuntu alpha 1 desktop ISOs are too large to fit on a CD. They can be burned to a DVD or USB stick, or you can install using the alternate ISOs.