>Интересно, что случилось с disk1 ? Он перестал быть загрузочным? http://www.freebsd.org/releases/7.2R/announce.html
Note: late in the testing cycle it was discovered some machines do not recognize the i386 disc1 as bootable (they just fall through to booting off the next boot device). All affected machines did see the other discs as bootable. If you have a machine with that problem booting off either bootonly or livefs and then swapping in disc1 once sysinstall starts should work.
Это косяк. Загрузитесь с бутонли и замените диск на диск1