VirtualCenter fails to start with SOAP error in log

It was a regular reboot but now Virtual Center will not start and looking in the logs we see this error:

2009-02-18 17:05:05.359 'App' 4260 warning VpxUtil Failed to parse XML in deserializing soap to object at 1: not well-formed (invalid token)
2009-02-18 17:05:05.359 'App' 4260 warning VpxdInvtHost::LoadHostHealthFromDb Failed todeserialize system health data from Db:

followed by a mass of XML which presumably is the bad SOAP packet, looking like this: <obj xmlns="urn:vim25" xsi:type="HealthSystemRuntime"><systemHealthInfo><numericSensorInfo><name>System Level for System Board 1</name><healthState><label>Green</label><summary>Green</summary><key>Green</key></healthState><currentReading>24800</currentReading><unitModifier>-2</unitModifier><baseUnits>Watts</baseUnits><sensorType>power</sensorType></numericSensorInfo><numericSensorInfo><name>Voltage 2 for Power Supply 2</name><healthState><label>Green</label><summary>Green</summary><key>Green</key></healthState><currentReading>23400</currentReading><unitModifier>-2</unitModifier><baseUnits>Volts</baseUnits><sensorType>voltage</sensorType></numericSensorInfo><numericSensorInfo><name>Voltage 1 for Power Supply 1</name><healthState><label>Green</label><summary>Green</summary><key>Green</key></healthState>

and on and on, there is heaps of it.....

further up the log stack are these lines:

2009-02-18 17:05:03.984 'Libs' 4260 warning VpxdOsLayer Couldn't read registry entry vmdbPort
2009-02-18 17:05:03.984 'Libs' 4260 warning VpxdOsLayer Couldn't read registry entry managedIP

are they relevant? The database is running and can be connected to by ODBC and trying a manual start of the virtualCenter server is no different to that of a boot-up.