Hello,
importing XEN VMs with VMware Converter is not supported (and not implemented), especially if they use paravirtualization. You may google and find some articles about how to do it manually.
If they don't use paravirtualization, you'll still have to do something manually, but it will be easier. The failure you experienced is during reconfiguration, which means all data have been successfully copied. Reconfiguration basically has three steps - installing GRUB, making the initrd, and fixing fstab. These usually can be done after booting the installation CD in a rescue mode.
HTH
Plamen