That error is not that helpful to pinpoint the problem. But, looks like there are few mandatory fields which are missing in on the flow rule might be in properties of flow shapes or other tabs in the rule. Can you open each shape and see if anything is missing in them and also check the other tabs
Thats the problem here. we are not getting any kind of useful error messages in the UI and the flow required parms in all the shapes are also specified. just posted this to know whether there are any others who experienced this kind of issue. By the way this is happening on the upgrade system from 6.1 SP2 to 7.1.9.