Hi Nick -thanks for the clear response.
Could you check that,
1) You are not over sysprepping? This will cause the image to fail to rearm. For example, I always script the install first, deploy the software and then sysprep. I never re-sysprep an image
2) Is VMware tools installed on your VMWare workstation. I've seen a post a while ago about someone reporting this giving issues with the rearm (as a general rule anyway, vmware tools should be avoided on gold images!)