If a Response.Redirect is opening inside of the tab you are probably making use of the TargetUrl property off the tab.  This would create iframe elements inside the tabs.  As with all frames, each frame will operate in its own context, as in it will not modify elements outside the frame.  In this case, to modify the location of the parent you can do it any number of ways all which will end up in using JavaScript. 

1. You can do it before going to the server.

2. You can redirect the tab contents to another page which will redirect the main page to some other url.

3. You can render a literal control which will redirect the main page.

All of these options will deal with working with the location property.  This is what is placed in the url bar of your browser window.  To access the main page from a page inside of a tab's iframe, you can do the following in BLOCKED SCRIPT

window.parent.document.location="Newpage.aspx";

Here is a Knowledge Base article that explains this some more with samples:

http://devcenter.infragistics.com/Support/KnowledgeBaseArticle.aspx?ArticleID=6688

Here are also some articles for accessing the frames from the main page and for accessing a frame from another frame respectively:

http://devcenter.infragistics.com/Support/KnowledgeBaseArticle.aspx?ArticleID=6689

http://devcenter.infragistics.com/Support/KnowledgeBaseArticle.aspx?ArticleID=6690