Hey,
Try setting the XmlLoadOnDemandType to Accumulative. The default setting of Synchronous does not work very well with full post backs. Accumulative will keep track of rows and such even after a full post back where as the default setting of Synchronous does not. It will load the first 50 rows so any click outside of that will not work.
this
.UltraWebGrid1.DisplayLayout.XmlLoadOnDemandType = Infragistics.WebUI.UltraWebGrid.XmlLoadOnDemandType.Accumulative;
Hope this helps.
XmlLoadOnDemandType
Thanks for this! After a good 3 weeks of searching on the net, I finally found the answer. This works now.