'virsh dominfo <VMID>' as well as 'virsh dumpxml <VMID>' returns 0 for Total (max) and Used (current) memory.

$ cat ovz.xml.4
<domain type='openvz' id='144'>
  <name>144</name>
  <vcpu>1</vcpu>
  <memory>524288</memory>
  <os>
    <type>exe</type>
    <init>/sbin/init</init>
  </os>
  <devices>
    <filesystem type='template'>
      <source name='centos-5-x86'/>
      <target dir='/'/>
    </filesystem>
    <interface type='bridge'>
      <source bridge='br0'/>
    </interface>
  </devices>
</domain>

$ virsh create ovz.xml.4

$ virsh dominfo 144
Id:             144
Name:           144
UUID:           fb213571-5674-f9d9-f3a3-3e13d23f350b
OS Type:        exe
State:          running
CPU(s):         1
CPU time:       44.5s
Max memory:     0 kB
Used memory:    0 kB
Persistent:     yes
Autostart:      enable

$ virsh dumpxml 144
<domain type='qemu' id='144'>              
  <name>144</name>                         
  <uuid>fb213571-5674-f9d9-f3a3-3e13d23f350b</uuid>
  <memory>0</memory>                               
  <currentMemory>0</currentMemory>                 
  <vcpu>1</vcpu>                                   
  <os>                                             
    <type>exe</type>                               
    <init>/sbin/init</init>                        
  </os>                                            
  <clock offset='utc'/>                            
  <on_poweroff>destroy</on_poweroff>               
  <on_reboot>destroy</on_reboot>
  <on_crash>destroy</on_crash>
  <devices>
    <filesystem type='template' accessmode='passthrough'>
      <source name='centos-5-x86'/>
      <target dir='/'/>
    </filesystem>
  </devices>
</domain>

Generated openvz config file:
ONBOOT="yes"

# UBC parameters (in form of barrier:limit)
KMEMSIZE="14372700:14790164"
LOCKEDPAGES="2048:2048"
PRIVVMPAGES="65536:69632"
SHMPAGES="21504:21504"
NUMPROC="240:240"
PHYSPAGES="0:unlimited"
VMGUARPAGES="33792:unlimited"
OOMGUARPAGES="26112:unlimited"
NUMTCPSOCK="360:360"
NUMFLOCK="188:206"
NUMPTY="16:16"
NUMSIGINFO="256:256"
TCPSNDBUF="1720320:2703360"
TCPRCVBUF="1720320:2703360"
OTHERSOCKBUF="1126080:2097152"
DGRAMRCVBUF="262144:262144"
NUMOTHERSOCK="360:360"
DCACHESIZE="3409920:3624960"
NUMFILE="9312:9312"
AVNUMPROC="180:180"
NUMIPTENT="128:128"

# Disk quota parameters (in form of softlimit:hardlimit)
DISKSPACE="1048576:1153024"
DISKINODES="200000:220000"
QUOTATIME="0"

# CPU fair scheduler parameter
CPUUNITS="1000"

#UUID: fb213571-5674-f9d9-f3a3-3e13d23f350b
VE_ROOT="/vz/root/$VEID"
VE_PRIVATE="/vz/private/$VEID"
OSTEMPLATE="centos-5-x86"
ORIGIN_SAMPLE="basic"
NAME="144"
NETIF="ifname=br0,bridge=br0,mac=52:54:00:1B:49:2F,host_ifname=veth144.0,host_mac=52:54:00:66:E2:E8"
CPUS="1"

$ vzcalc -v 144
Resource     Current(%)  Promised(%)  Max(%)
Low Mem          0.29       6.16       6.16
Total RAM        0.44        n/a        n/a
Mem + Swap       0.14       2.02        n/a
Alloc. Mem       0.23       2.52       4.81
Num. Proc        0.04        n/a       0.74
--------------------------------------------
Memory           0.44       6.16       6.16

software used:
ovzkernel release is 2.6.18-194.26.1.el5.028stab081.1,
vzctl-3.0.26-1,
OS is CentOS 5.5,
libvirt/virsh version is 0.8.8.

I set a severity for that bug to 'urgent' since it makes impossible to track host resource utilization by libvirt/virsh means.