In POST:
http://post-office.corp.redhat.com/archives/rhvirt-patches/2011-April/msg00440.html

tested with 
libvirt-0.8.2-19.el5
kernel-2.6.18-259.el5
xen-3.0.3-130.el5

# for i in `seq 1000`; do  virsh save --domain pv --file /opt/pv.save;
virsh restore /opt/pv.save; done


# for i in `seq 1000`; do  virsh save --domain hvm --file /opt/hvm.save;
virsh restore /opt/hvm.save; done

All of the above command get on error during the 1000 times tight loop . 

So set bug status to VERIFIED

Could not reproduce this bug on the following components of rh5.6: 
kernel-2.6.18-238.el5
xen-3.0.3-120.el5
libvirt-0.8.2-15.el5

Steps:
# cat test2.sh 
for i in `seq 1000`;
 do  
virsh save --domain rh5.6 --file /opt/pv.save;
echo $i;
virsh restore /opt/pv.save; 
done

# sh test2.sh > result.txt
# cat result.txt
...
998
Domain restored from /opt/pv.save

Domain rh5.6 saved to /opt/pv.save

999
Domain restored from /opt/pv.save

Domain rh5.6 saved to /opt/pv.save

1000
Domain restored from /opt/pv.save

Note: all success

An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.

http://rhn.redhat.com/errata/RHSA-2011-1019.html