freebsd stable - May 2011 - trying to dump core, hangs the kernel

Hi,

A new box I have installed cannot dump core. It seems hung,
I cannot cannot break into the debugger, after calling doadump().

Physical memory: 943 MB
Dumping 60MB:

This is 8.2-RELEASE-p1.

It has this (probably cheap) SATA controller, in case it matters:
atapci1@pci0:0:31:1:    class=0x010601 card=0x52871849 chip=0x528710b9 
rev=0x02 hdr=0x00
     vendor     = 'Acer Labs Incorporated (ALi/ULi)'
     device     = 'SATA/Raid controller (ULI M1573)'
     class      = mass storage
     subclass   = SATA

Thanks in advance for any help,

Nikos