Sync Problems

I have a LTM 1600 and a VE esxi guest which I'm trying to cluster/sync. I have the peering working, and a device group created but when I attempt a sync I get the following error:

 

Sync error on dcsltm01: Load failed from dcsltm02v 01070734:3: Configuration error: vmw-compat: vlan may only have one interface. Recommended action: Review the error message and determine corrective action on the device

 

There is precisely no information around on this error. I have just a single 'internal' interface, which is a single vlan on a single interface (on each of the devices) with one self IP. Any ideas what the error would be refering to given the above information?

 

Cheers