Greetings,
I also had this problem with a YRC1000 micro ethernet i/p comunications to an omron NX102.
I found the problem was in network configurator that the output and input instances need to be reversed from what is displayed in the Motoman controller.
(ie. in YRC 1000 input instance is 50 and output instance is 100 then in network configurator input instance needs to be 100 and output instance needs to be 50).
Andrew