Hello Bujji,

To be able to help you on such a situation we would need a lot more information. E.g. DNN version used, type of installation: local or hostingsituation, single portal?, hardware/ software, database type, what kind of skin were you using (default dnn or custommade) etc. As you see the error you got can have many diferent causes and is a rather common and generic DNN error. Causes can only be excluded or found if enough information is provided.

In this particular case it could be that there is some object missing in the code of the Skin file (check directory: portals/_default/Skins/ [skindirectory: .ascx file]. Maybe it's the missing login object: <%@ Register TagPrefix="dnn" TagName="LOGIN" Src="~/Admin/Skins/Login.ascx" %> and <dnn:LOGIN runat="server" id="dnnLOGIN" />
If you cannot find these two pieces of code in your skinfile, please add them and try again.

Meanwhile we hope you've been able to solve you problem by now. For future items you can ofcourse visit our forums anytime.