Hi James,
The error which you have mentioned, is an indication of threading issues. Are there multiple threads involved in your appilcation? If so, please check the Knowledge Base(KB) article link below.
http://www.syncfusion.com/support/kb/grid/Default.aspx?ToDo=view&questId=78Intermittant errors can be indications of threading issues. Any calls into the grid must be done on the thread that creates it, and you can use grid.InvokeRequired to check for this.
Here is a sample.
LoadDataBackGroundThreadBest Regards,
Haneef