Comment 2 for bug 533358

The same crash occurs (for me repeatedly at 24%) if you install direct from the Live CD without trying Ubuntu first. If you have wireless internet only, obviously it won't be configured at installation time so Ubiquity hangs after user selects 'Update this installer'.

Is it possible for Ubiquity to check if an active internet connection is available and if not, hide the 'Update this installer' button?

It does work over wifi however, if you run the live CD, configure the wifi and then choose to install permanently afterwards.