2 or more users can see same info

I'm using ASP.NET with Telerik controls, also I'm using an architecture of 3 tiers and Webforms. When I'm on localhost the page works well, but when I uplodad it to my server, if 2 or more users use the page, every user can see what other user do.

I mean: Exist User A,B and C. The user A populate a radgrid, the users B and C can see the info of user A.

Also if user A and B uses the same process, and populate the grid all useres can see what info uses each user.

Why it happens, and how can I fix it?

Regards!