old server esx 4.1 new esxi5.0
These are the host versions, but what version of vCenter are you running?
If you use these kind of cold migrations via vCenter, it will choose the management interfaces according to how they are registered within vCenter.
Consider the following:
You have Host A and B which have two management interfaces with the respective IPs AX/AY and BX/BY. You registered your hosts in vCenter with IP AX and BX (or through a DNS-name that points to these IPs). The result is that the cold migration process will only take place between these two IPs. The other interfaces are not considered for cold migrations.
If you have registered the hosts via DNS-names, it might work if you temporarily alter the local /etc/hosts file on both hosts with AY and BY of the respectively other host.
Apart from that, you could create a VM on the crossover network that acts as a V2V server with VMware Converter, connecting to both hosts via their AY and BY IP to do a V2V conversion of the target VM over this crossover network.