This error comes from the Vmware jtoolkit jar which is used by vCenter data collector. It will not effect any functionality. No need to worry.
Please let us know if you need more information.
I suspected as much, but it is great to have it confirmed.
We have been having some issues with the stats collection jobs failing and turning the status of the collector to down, so I was trying to wade through the voluminous logs and noticed these ERROR messages occurring regularly. One less thing to look into now