Xen users - Jun 2013 - because the domU to get vcpu = 100%, it becomes inoperative

Hello
I have a
  dom0: 1GB RAM, Q8400 CPU, Distro SLES11SP2 Distro with kernel
3.0.13-0.27-xen and xen-4.1.2_14-0.5.5
  domU: paravirtualized with 3GB RAM and Distro SLES11SP1  with kernel
2.6.32.12-0.7-xen and running alone zabbix 1.8.7 and
mysql-5.0.67-13.20.1


  It sometimes happens that the domU cpu reaches 101% (seen from xm
top) and domU becomes inoperative (can not enter via ssh nor console
of virt-manager)
  I do not understand this behavior, l 4 vcpu domU is configured, do
not understand why the cpu=100% is saturated, if your maximum should
be 400%
  From the domU only has 25% cpu consumption.

  I must have something misconfigured, but it''s not ..

in https://docs.google.com/file/d/0B8rkUchOnWAKMV91OFZ6VnlYTms/edit?usp=sharing
 this the log

Thanks for reading and excuse the English ...