Hello Manoj,
This certainly does not look like the correct and expected behaviour. Still, I remember a bug like this recently (I believe it was when the grid was with fixed columns) that has been addressed. Are you using the latest hotfix of UltraWebGrid? If not, upgrading to the latest would certainly be a good idea.
If this does not help, I believe the best way to proceed in situations like this is to contact our Developer Support folks directly, if possible, with a small subset of your project reproducing the issues, so that they can hopefully provide additional details:
http://es.infragistics.com/support/