Hi Kiran,
Can you post a screen shot? Just attach an image file to your post (under the Options tab) and it will display as an image in the thread.
Hm. I can't see any reason why that would happen. Does the same thing happen if you hide and then re-show one of the columns that is already visible?
Your best bet is probably to duplicate this behavior in a small sample project and Submit an incident to Infragistics Developer Support so they can check it out.