Engadget reports that the latest Ubuntu alpha is killing Intel network cards by corrupting the NVRAM used to store MAC addresses. According to the article, the ISO hasn't been pulled but warning has been added:

Well, it looks like the good times that are the Ubuntu alpha testing process hit a bit of a snag recently, as one of the latest kernels apparently had the nasty side effect of irreparably damaging some users' hardware -- specifically, certain Intel network cards. So far, it seems that only laptops have been affected by the bug, which corrupts the NVRAM used to store data like MAC addresses, but folks don't seem to be ruling out the possibility that it could affect desktops as well. What's more, while a warning has been added to the ISO download, it hasn't been pulled altogether, with the only explanation given being that it would delay the 8.10 release schedule too much. Not entirely surprisingly, that has prompted at least a few folks to give up on testing alpha versions of the OS, at least until this whole thing gets sorted out.

So that's why it's called an alpha :-)