hello,
i also have the ga-7n400 pro 2 and am seeing hard locks. i have had it lock with mandrake 9.0, 9.2, win2k and during the gentoo 1.0 install. i am suspecting the gigabit on-board lan because it seems to happen when transferring lots of data from another computer and talking to that computer via ssh, etc. i hung gentoo right at the start with their script "net-setup eth0" => dead. i installed a PCI 10/100 network card and disabled the on-board lan, but the OSes still appear to be talking to the on-board lan or something to see what it is.
i'm interested to hear what you found. i'm going to try the <CTRL>-F1 trick to get into the "secret" BIOS settings and see what i find.
thanks,
-sean