I revently got this error after trying to clone a cloned copy of a CentOS 5.6 VM.
I imported CentOS OVF from scratch, updated tools and hardware and cloned from template in vCenter and no problem.
If I then tried to clone from the cloned copy I got this error. Not sure if this helps. To resolve my issue I re imported the OVF again and cloned from that. Had to do some rework in the base VM but it ended up working.