Hi Andre,
We are using thin provisioning at both the ESX and SAN level. I think you are right in that this must have been what occurred. Obviously thick provisioning the average volume really isn't an effective approach, I guess over-provisioning to the point of being positive the volume.
However I am surprised that the default action would be to pause the OS if the volumes are not even on the OS drive. This seems counter-productive although I understand why that might happen. I guess maybe it makes sense not to thin-provision data volumes on VMDK but rely on SAN thin-provisioning for those same volumes instead.