Originally Posted by villegente
But when I try to boot, I have the message : can not dump, no dump device defined.
When the kernel panics it tries to do a core dump, that is, copy the contents of memory to a file for later examination with debugging tools. When this happens before the root filesystem is mounted or when there's any other problem writing the file you'll see the message above.
Kernel panics usually indicate a hardware problem, common causes are usb devices, hard drives and memory plus all the usual things like overheating.
The last time I saw this was when a usb flash drive was not properly unmounted, on next boot the kernel panicked, simply removing the drive and rebooting solved the problem.
I'd suggest unplugging any usb devices first, if that doesn't work you'll need to go through your hardware and make sure it's both compatible with PCBSD/FreeBSD and that nothing is faulty.