Hi,
Problem
I had a problem while synchronizing with the ArcGIS Mobile 10.0 Application.
For one layer I always get a "ESRI.ArcGIS.Mobile.MobileServices.RequestException". A look in the ErrorCode property shows a "ESRI.ArcGIS.Mobile.MobileServices.RequestErrorCode.SaveEditsFatalError".
The feature class is non versioned but has a Global_Id set.
The error does not appears on every client, only for some.
When deleting the cache and creating a new one, everything is fine (except the data which are lost).
Because I did not find anything matching to my problem in the internet, I will show the answer here for any other people having the same problem. Maybe it helps you.
Solution
One field in the feature class was defined as not null. In the application this field was filled in some cases with an empty string ("").
While this seems not to be a problem for the API, it is a problem when storing in the geodatabase. This causes the problem.
When I changed the value of this field to a valid string value, the synchronization was successful.
I my opinion this is a bug.