While these responses have all been very helpful and thoughtful, none has resolved this issue.
But, I do appreciate the responses and for keeping me on track.
I've upgraded all esx and esxi hosts to the same buld - 4.1 update 1
I've put vmotion on its own separate vlan and it is sharing a teamed pair of nics (POrt ID) with the service console. Both 1 GB full.
I changed three esx hosts that were using IP Hash to Port ID for the service sonsole/vmotion vmnics
But I still have the same problem. vmotin works fine until I vmotion from an esxi to an esx host. The esxi hosts are newer with a slightly different cpu, the model is the same, and the esxi hosts are on one physucal cisco switch , while the esx hosts are on another.
I'm about to connect a crossover cable between two servers and see if I still have the same problem.
vmotion works OK between esx hosts and between esxi hosts. It also works ok from esx to esxi. But going from esxi to esx is excrucuatingly slow. A 16 GB ram VM will vmotion successfully , but it will take 2 hours. A 2 GB VM that takes 1 min anythere else takes 15-20 minutes.
Thanks again!
Tom