Everything was smooth before i upgrade VirtualBox to version 3.0.12, i can not install a 64bit os, even unables to startup a installed os base on 64bit.

The screen show the error message “NMI Watchdog detected LOCKUP”, and i found this via google:
and a guy called kevin.clevenger gave the solution:

Setting the kernel parameter nmi_watchdog=0 (as suggested in another post) works around the issue and gets the client booted. I do not consider this to be a fix however.

1) install the CentOS 5.4 x86_64, boot: linux text nmi_watchdog=0
2) startup the OS, when you see boot loader then press “a” to modify the default boot, add nmi_watchdog=0 in the end, continue booting. this change is only okay for the current boot,  so i suggest editing the “/boot/grub/grub.conf”,  and add the “nmi_watchdog=0” at the end of  the line witch looks like:  kernel /vmlinuz-2.6.18-164.el5 ro root=/dev/VolGroup00/LogVol00 nmi_watchdog=0