I think Avinash got it right, debian is not supported
I have some experience with migrating vms from xenserver to vmware,
I used this method and I guess you can do that too (I'll describe it in general)
1. boot a debian vm on vmware in rescue mode
2. create the same partitions / disk setup you have in the xen vms
3. format it and mount it
4. start networking and ssh
5. transfer the whole disk with something like "cd / ; tar cf - . | ssh root@vmmachine "cd /mnt ; tar xvf -""
6.install "generic kernel" ( xen vms have xen based kernel) - chroot /mnt ; apt-get install linux-image-generic
7.change to boot from generic kernel
8.fix grub with grub-install --recheck ( or use grub -> setup (hd0,0) )
good luck 
or just reinstall